UPSC Science & Technology PYQs (2014-25) with Solved Answers

GENERAL SCIENCE

 

Which one of the following is synthesized in the human body that dilates blood vessels and increases blood flow UPSC CSE Prelims 2024

a Nitric oxide
 b Nitrous oxide
 c Nitrogen dioxide
 d Nitrogen pentoxide

Answer

a Nitric oxide

Detailed Explanation

●     Nitric oxide NO is a naturally synthesized molecule in the human body that plays a crucial role in vasodilation the widening of blood vessels

●     It is produced by the endothelium inner lining of blood vessels from the amino acid L-arginine through the action of the enzyme nitric oxide synthase NOS

●     Mechanism Nitric oxide activates the enzyme guanylate cyclase leading to the production of cyclic GMP cGMP which relaxes smooth muscle cells resulting in increased blood flow

●     This process is essential for regulating blood pressure preventing clot formation and ensuring efficient oxygen delivery to tissues

Why are the other options incorrect

b Nitrous oxide N2O Commonly known as laughing gas used in anesthesia but it does not dilate blood vessels in the human body
 c Nitrogen dioxide NO2 A harmful air pollutant not synthesized in the body
 d Nitrogen pentoxide N2O5 A highly reactive compound not involved in physiological processes

Thus the correct answer is a Nitric oxide

2.  Consider the following statements in respect of probiotics:

1. Probiotics are made of both bacteria and yeast.
   
   
2. The organisms in probiotics are found in foods we ingest, but they do not naturally occur in our gut.
   
   
3. Probiotics help in the digestion of milk sugars.
   
   

Which of the statements given above is/are correct? [UPSC CSE Pre 2021]
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (c)

Explanation:

• Statement 1 is correct: Probiotics consist of live microorganisms, including both bacteria and yeast, that provide health benefits when consumed. The most commonly used probiotic bacteria belong to the Lactobacillus and Bifidobacterium genera, while Saccharomyces boulardii is an example of a probiotic yeast.
  
  
• Statement 2 is incorrect: Some probiotic bacteria are naturally present in the human gut. For example, Lactobacillus acidophilus, Bifidobacterium bifidum, and Saccharomyces boulardii naturally inhabit the intestines and help maintain gut health. Therefore, the claim that probiotics do not naturally occur in the gut is incorrect.
  
  
• Statement 3 is correct: Probiotics help break down lactose (milk sugar) into simpler sugars like glucose and galactose. This is especially beneficial for people with lactose intolerance, as probiotics contain enzymes like β-D-galactosidase, which assist in digesting dairy products.
  
  

Thus, Option (c) – 1 and 3 only – is the correct answer.

2. Which one of the following statements best describes the role of B cells and T cells in the human body? [UPSC CSE Pre 2022]

(a) They protect the body from environmental allergens.
 (b) They alleviate the body's pain and inflammation.
 (c) They act as immunosuppressants in the body.
 (d) They protect the body from diseases caused by pathogens.

Solution: (d)

Explanation:

• B cells and T cells are crucial components of the adaptive immune system, which protects the body from pathogens.
  
  
• T cells (T lymphocytes):
  
  
  • These cells mature in the thymus and are responsible for cell-mediated immunity.
    
    
  • They help destroy infected or cancerous cells and regulate immune responses.
    
    
  • They also assist in activating B cells to produce antibodies.
    
    
• B cells (B lymphocytes):
  
  
  • These cells mature in the bone marrow and are responsible for humoral immunity.
    
    
  • They produce antibodies that neutralize pathogens, preventing them from infecting healthy cells.
    
    
  • Once a pathogen enters the body, B cells recognize and bind to it, producing antibodies that help eliminate the infection.
    
    

Since B and T cells protect the body from diseases caused by pathogens (bacteria, viruses, fungi, etc.), Option (d) is the correct answer.

3. Certain species of which one of the following organisms are well known as cultivators of fungi? [UPSC CSE Pre 2022]

(a) Ant
 (b) Cockroach
 (c) Crab
 (d) Spider

Solution: (a)

Explanation:

• Certain species of ants, such as leafcutter ants, are known for cultivating fungi as a food source.
  
  
• Leafcutter ants cut pieces of leaves and carry them back to their nests, where they use them as a substrate for growing fungi.
  
  
• The ants feed on the cultivated fungi, which in turn rely on the decomposing leaf material provided by the ants.
  
  
• This is an example of a mutualistic relationship, where both ants and fungi benefit.
  
  

Cockroaches, crabs, and spiders do not exhibit such behavior, so Option (a) – Ant – is the correct answer.

4. Which of the following have species that can establish symbiotic relationships with other organisms? [UPSC CSE Pre 2021]

1. Cnidarians
   
   
2. Fungi
   
   
3. Protozoa
   
   

Select the correct answer using the code given below:
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (d)

Explanation:

• Cnidarians:
  
  
  • Includes corals and jellyfish.
    
    
  • Many corals have a mutualistic relationship with zooxanthellae algae. The algae provide food via photosynthesis, while the coral provides shelter.
    
    
• Fungi:
  
  
  • Can form mycorrhizal relationships with plants, helping them absorb nutrients.
    
    
  • Fungi also form lichens, a mutualistic partnership with algae or cyanobacteria.
    
    
• Protozoa:
  
  
  • Some protozoa in the gut of termites help digest cellulose, enabling termites to feed on wood.
    
    

Since all three groups can form symbiotic relationships, Option (d) – 1, 2, and 3 – is correct.

5. Which of the following can be cultured in artificial/synthetic medium? [UPSC CSE Pre 2021]

1. Bacteria
   
   
2. Fungi
   
   
3. Virus
   
   

Select the correct answer using the code given below:
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (a)

Explanation:

• Bacteria:
  
  
  • Can be cultured on nutrient agar or liquid broth under controlled laboratory conditions.
    
    
  • Provides nutrients like carbon, nitrogen, and salts for bacterial growth.
    
    
• Fungi:
  
  
  • Can be grown on Sabouraud’s agar or other specialized media.
    
    
  • Requires sugar sources and moisture to grow.
    
    
• Viruses:
  
  
  • Cannot be cultured in artificial media as they require a host cell to replicate.
    
    
  • Viruses are obligate intracellular parasites and must infect a living cell (e.g., bacteria, plant, or animal cell) to reproduce.
    
    

Thus, Option (a) – 1 and 2 only – is the correct answer.

6. In nature, which of the following is/are most likely to be found surviving on a surface without soil? [UPSC CSE Pre 2021]

1. Fern
   
   
2. Lichen
   
   
3. Moss
   
   
4. Mushroom
   
   

Select the correct answer using the code given below:
 (a) 1 and 4 only
 (b) 2 only
 (c) 2 and 3 only
 (d) 1, 3 and 4 only

Solution: (c)

Explanation:

Some organisms can grow on surfaces without requiring soil, while others need soil or organic matter for survival.

• Fern (Incorrect)
  
  
  • Ferns are vascular plants that require moist soil to grow.
    
    
  • They need good drainage and organic matter for nutrients.
    
    
  • Thus, ferns are unlikely to grow directly on a surface without soil.
    
    
• Lichen (Correct)
  
  
  • Lichens are a symbiotic association between fungi and algae.
    
    
  • They can grow on surfaces such as rocks, trees, metal, or glass without requiring soil.
    
    
  • They absorb moisture from the air and use photosynthesis for food.
    
    
• Moss (Correct)
  
  
  • Mosses are non-vascular plants that grow in damp environments.
    
    
  • They do not require true roots and can grow directly on rocks, tree bark, and rooftops.
    
    
  • Since mosses can grow on non-soil surfaces, they are included in the answer.
    
    
• Mushroom (Incorrect)
  
  
  • Mushrooms are the fruiting bodies of fungi.
    
    
  • They require decaying organic matter (substrate) to grow, such as dead leaves, wood, or compost.
    
    
  • Mushrooms do not grow directly on bare surfaces like rocks without a nutrient source.
    
    

Thus, Option (c) – Lichen and Moss – is the correct answer.

7. In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? [UPSC CSE Pre 2021]

1. Area of the hole in the lid
   
   
2. Temperature of the flame
   
   
3. Weight of the lid
   
   

Select the correct answer using the code given below:
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (c)

Explanation:

A pressure cooker works by increasing the internal pressure, which raises the boiling point of water and speeds up cooking.

• Option 1: Area of the hole in the lid (Correct)
  
  
  • The hole (or vent) in the lid controls how much steam escapes from the cooker.
    
    
  • A smaller hole retains more steam inside, increasing pressure and raising the boiling point of water.
    
    
  • A larger hole allows more steam to escape, reducing the pressure and lowering the cooking temperature.
    
    
• Option 2: Temperature of the flame (Incorrect)
  
  
  • The flame’s temperature affects how quickly the cooker reaches the desired pressure, but it does not change the cooking temperature itself.
    
    
  • Once the cooker reaches its working pressure, the internal temperature remains constant, whether the flame is high or low.
    
    
• Option 3: Weight of the lid (Correct)
  
  
  • The weight of the lid helps maintain pressure inside the cooker.
    
    
  • A heavier lid increases the pressure inside, leading to a higher boiling point and faster cooking.
    
    
  • A lighter lid allows steam to escape more easily, reducing the pressure and keeping the cooking temperature lower.
    
    

Thus, Option (c) – 1 and 3 only – is the correct answer.

8. With reference to furnace oil, consider the following statements: (UPSC CSE Pre 2021)

1. It is a product of oil refineries.
2. Some industries use it to generate power.
3. Its use causes sulphur emissions into the environment.

Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (d)
Explanation:

• Furnace oil is a residual fuel obtained from crude oil refining.
• Industries use it in boilers and furnaces for power generation.
• Burning furnace oil releases sulphur compounds, contributing to air pollution and acid rain.

9. Why is there a concern about copper smelting plants? (UPSC CSE Pre 2021)
10. They may release lethal quantities of carbon monoxide into the environment.
11. The copper slag can cause the leaching of some heavy metals into the environment.
12. They may release sulphur dioxide as a pollutant.

Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (b)
Explanation:

• Copper smelting does not release lethal quantities of carbon monoxide as a direct byproduct.
• Copper slag contains heavy metals like arsenic and lead, which may leach into the environment.
• Sulphur dioxide is a major byproduct of copper smelting, contributing to acid rain and respiratory issues.

10. Bisphenol A (BPA), a cause of concern, is a structural/key component in the manufacture of which of the following kinds of plastics? (UPSC CSE Pre 2021) (a) Low-density polyethylene
    (b) Polycarbonate
    (c) Polyethylene terephthalate
    (d) Polyvinyl chloride

Solution: (b)
Explanation: BPA is primarily used in polycarbonate plastics, known for their transparency and high impact resistance, commonly found in food containers and medical devices.

11. Water can dissolve more substances than any other liquid because: (UPSC CSE Pre 2021) (a) It is dipolar in nature
    (b) It is a good conductor of heat
    (c) It has high value of specific heat
    (d) It is an oxide of hydrogen

Solution: (a)
Explanation: Water's dipolar nature allows it to interact with and dissolve various substances due to its positive and negative charges attracting different molecules.

12. Which one of the following is a reason why astronomical distances are measured in light-years? (UPSC CSE Pre 2021) (a) Distances among stellar bodies do not change.
    (b) Gravity of stellar bodies does not change.
    (c) Light always travels in a straight line.
    (d) Speed of light is always the same.

Solution: (d)
Explanation: The speed of light is constant, making it a reliable unit for measuring vast cosmic distances.

13. Which of the following statements are correct regarding the general differences between plant and animal cells? (UPSC CSE Pre 2020)
14. Plant cells have cellulose cell walls, while animal cells do not.
15. Plant cells do not have plasma membranes, unlike animal cells.
16. Mature plant cells have one large vacuole, while animal cells have many small vacuoles.

Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (c)
Explanation:

• Plant cells have cellulose walls for rigidity, unlike animal cells.
• Both plant and animal cells have plasma membranes, making statement 2 incorrect.
• Plant cells typically contain one large vacuole, whereas animal cells have multiple smaller ones.

14. Steel slag can be used for which of the following? (UPSC CSE Pre 2020)
15. Construction of base roads
16. Improvement of agricultural soil
17. Production of cement

Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (d)
Explanation: Steel slag is used in road construction, soil improvement, and cement production due to its durability and nutrient content.

15. Goldsmiths blow the outermost zone of a flame with a metallic blow-pipe for melting gold and silver. For which one of the following reasons do they use the outermost zone of the flame? [UPSC CSE Pre. 2020]

(a) It is the hottest part providing most heat.
 (b) This luminous zone doesn't produce any ash.
 (c) It is the least-hottest part protecting the design of jewelry.
 (d) The middle zone vaporizes gold, leading to loss of metal.

Solution: (a)
 Explanation:
 The substances that vaporize during burning produce flames. For example, kerosene oil and molten wax rise through the wick, vaporize during burning, and form flames, whereas charcoal does not vaporize and thus does not produce a flame.

The outermost zone of the flame is the hottest part, ensuring maximum heat during burning, which facilitates quick melting of gold and silver. Complete combustion occurs in this zone, preventing blackening of the metal.

• Option (b) is incorrect because the outermost part of the flame is the non-luminous zone, which is blue in color. The luminous zone is the middle portion, which contains unburnt carbon particles that could deposit on the metal.
  
  
• Option (c) is incorrect because the innermost zone is the least hot and contains unburnt wax vapors. The outermost zone provides the required heat for melting gold.
  
  
• Option (d) is incorrect because gold requires a very high temperature for vaporization, which is not possible in regular flames. The middle portion is only moderately hot and contains unburnt products due to partial combustion.
  
  

16. The word 'Denisovan' is sometimes mentioned in media in reference to: [UPSC CSE Pre. 2019]

(a) fossils of a kind of dinosaurs
 (b) an early human species
 (c) a cave system found in North-East India
 (d) a geological period in the history of the Indian subcontinent

Solution: (b)
 Explanation:
 Denisovans were an extinct species or subspecies of archaic humans that existed across Asia during the Lower and Middle Paleolithic periods. Their fossils were discovered in the Denisova Cave in Siberia, Russia.

Denisovans were closely related to Neanderthals and modern humans, but they had distinct physical features, including a broad skull, a protruding lower jaw, and a sloping forehead.

They interbred with both Neanderthals and modern humans, and their DNA has been found in various populations worldwide, particularly among Southeast Asians and Australasians. This suggests that Denisovans played a significant role in human evolution.

17. Which one of the following statements is not correct? [UPSC CSE Pre. 2019]

(a) Hepatitis B virus is transmitted much like HIV.
 (b) Hepatitis B, unlike Hepatitis C, does not have a vaccine.
 (c) Globally, the number of people infected with Hepatitis B and C viruses is several times more than those infected with HIV.
 (d) Some of those infected with Hepatitis B and C viruses do not show symptoms for many years.

Solution: (b)
 Explanation:

• Option (b) is incorrect because there is a vaccine for Hepatitis B, whereas there is no vaccine for Hepatitis C. The Hepatitis C virus is highly variable, making vaccine development difficult.
  
  
• The Hepatitis B vaccine is sometimes called the first "anti-cancer" vaccine because it prevents Hepatitis B, which is a leading cause of liver cancer worldwide.
  
  
• Option (a) is correct as Hepatitis B is transmitted similarly to HIV, primarily through blood, sexual contact, and from mother to child during childbirth.
  
  
• Option (c) is correct because Hepatitis B and C infections are much more common globally than HIV infections.
  
  
• Option (d) is correct as many infected individuals remain asymptomatic for years, increasing the risk of unknowingly transmitting the virus.

18. With reference to recent developments in science, which one of the following statements is not correct? [UPSC CSE Pre. 2019]

(a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
 (b) Pieces of artificial functional DNA can be created in laboratories.
 (c) A piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory.
 (d) Cells taken out from plants and animals can be made to undergo cell division in laboratory petri dishes.

Solution: (a)
 Explanation:

• Statement (a) is incorrect. While DNA segments from different species can be joined, the creation of fully functional chromosomes from such segments has not yet been achieved.
  
  
• Statement (b) is correct. Unlike DNA synthesis in living cells, artificial gene synthesis does not require a template DNA, enabling the synthesis of virtually any DNA sequence in laboratories.
  
  
• Statement (c) is correct. A piece of DNA extracted from an animal cell can be replicated outside a living cell under laboratory conditions.
  
  
• Statement (d) is correct. With suitable conditions, most plant and animal cells can survive, divide, and express differentiated properties in tissue culture dishes. This allows researchers to study their behavior under controlled conditions.
  
  

19. Consider the following statements: [UPSC CSE Pre. 2018]

1. Light is affected by gravity.
   
   
2. The Universe is constantly expanding.
   
   
3. Matter warps its surrounding space-time.
   
   

Which of the above is/are the prediction(s) of Albert Einstein's General Theory of Relativity, often discussed in media?

(a) 1 and 2 only
 (b) 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:
 Albert Einstein’s General Theory of Relativity predicts all three statements:

• Statement 1 is correct. According to this theory, light is affected by gravity in the same way that matter is. This was confirmed by gravitational lensing, where light bends around massive objects like stars and black holes.
  
  
• Statement 2 is correct. Based on this theory, Edwin Hubble discovered that distant galaxies move away faster than closer ones, confirming the universe is expanding.
  
  
• Statement 3 is correct. The theory states that gravity is caused by the warping of space and time by massive objects, which influences the movement of nearby objects. This curvature of spacetime determines the path that light and matter follow.
  
  

Thus, all three statements are valid predictions of Einstein’s General Theory of Relativity.

20. What is the reason for non-metals being bad conductors of electricity? [UPSC CSE Pre. 2018]

(a) High melting point at normal temperature
 (b) Excessive free protons around the nucleus
 (c) Absence of readily available free electrons
 (d) Low resistance to external factors

Solution: (c)
 Explanation:

• Option (c) is correct. Electrical conduction occurs due to the movement of free electrons. Metals are good conductors because their atoms lose their outermost electrons, forming a structure where free electrons move easily.
  
  
• Non-metals, on the other hand, hold their electrons tightly to the nucleus, preventing free electron movement. This absence of readily available free electrons makes them poor conductors.
  
  
• Option (a) is incorrect because a high melting point does not determine electrical conductivity. Some high-melting metals, like tungsten, are still good conductors.
  
  
• Option (b) is incorrect because protons do not contribute to electrical conduction; electrons do.
  
  
• Option (d) is incorrect because non-metals generally have high resistance to electricity, not low resistance.
  
  

However, certain non-metals like graphite (a form of carbon) can conduct electricity due to delocalized electrons in its structure.

21. Consider the following pairs: [UPSC CSE Pre. 2017]

Commonly used/consumed materials	Unwanted or controversial chemicals likely to be found in them
1. Lipstick	Lead
2. Soft Drinks	Brominated vegetable oils
3. Chinese fast food	Monosodium glutamate (MSG)

Which of the pairs given above is/are correctly matched?

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:

• Pair 1 is correctly matched. Lead is a common impurity in lipsticks and other cosmetics (e.g., eye shadows, blushes, powders, shampoos, lotions). Though regulations limit its presence, trace amounts have been detected in many products.
  
  
• Pair 2 is correctly matched. Brominated vegetable oil (BVO) is used as an emulsifier in soft drinks to prevent citrus flavoring from separating. However, due to health concerns, it has been banned in Europe and Japan.
  
  
• Pair 3 is correctly matched. Monosodium Glutamate (MSG) is commonly used in Chinese fast food to enhance flavor. Some studies suggest it has neuro-excitatory effects and may cause headaches or allergic reactions in some people.
  
  

Thus, all three pairs are correctly matched, making option (d) the correct answer.

22. Which of the following statements is/are correct? Viruses can infect: [UPSC CSE Pre. 2016]

1. Bacteria
   
   
2. Fungi
   
   
3. Plants
   
   

Select the correct answer using the code given below:
 (a) 1 and 2 only
 (b) 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:
 Viruses are classified based on the hosts they infect:

• Bacteriophages are viruses that infect bacteria.
  
  
• Mycoviruses infect fungi.
  
  
• Plant viruses (e.g., Cauliflower Mosaic Virus) infect plants.
  
  
• Animal viruses, such as the Polio virus and Retrovirus, infect humans and other animals.
  
  

Thus, all three statements are correct.

23. Consider the following pairs: [UPSC CSE Pre. 2014]

Vitamin	Deficiency Disease
1. Vitamin C	Scurvy
2. Vitamin D	Rickets
3. Vitamin E	Night blindness

Which of the pairs given above is/are correctly matched?

(a) 1 and 2 only
 (b) 3 only
 (c) 1, 2, and 3
 (d) None of the above

Solution: (a)
 Explanation:

• Pair 1 is correctly matched. Vitamin C deficiency causes Scurvy, characterized by bleeding gums, fatigue, and skin issues due to impaired collagen synthesis.
  
  
• Pair 2 is correctly matched. Vitamin D deficiency leads to Rickets in children, causing bone deformities due to impaired calcium absorption.
  
  
• Pair 3 is incorrectly matched. Night blindness is caused by Vitamin A deficiency, not Vitamin E. Vitamin E is primarily associated with immune function and reproduction, not vision.
  
  

Thus, option (a) is correct.

Additional Vitamin Deficiency Diseases:

• Vitamin A → Night blindness
  
  
• Vitamin B1 (Thiamine) → Beriberi
  
  
• Vitamin B2 (Riboflavin) → Ariboflavinosis
  
  
• Vitamin B3 (Niacin) → Pellagra
  
  
• Vitamin B5 (Pantothenic acid) → Paresthesia
  
  
• Vitamin B6 (Pyridoxine) → Anemia
  
  
• Vitamin B7 (Biotin) → Dermatitis, enteritis
  
  
• Vitamin B9/B12 → Megaloblastic anemia
  
  
• Vitamin K → Blood clotting issues
  
  

24. Which of the following is/are example(s) of chemical change? [UPSC CSE Pre. 2014]

1. Crystallization of sodium chloride
   
   
2. Melting of ice
   
   
3. Souring of milk
   
   

Select the correct answer using the code given below:
 (a) 1 and 2 only
 (b) 3 only
 (c) 1, 2, and 3
 (d) None of the above

Solution: (b)
 Explanation:

• Option 1 is incorrect. Crystallization of sodium chloride is a physical change, as it only involves a change in state, not a chemical transformation.
  
  
• Option 2 is incorrect. Melting of ice is also a physical change, as water remains chemically the same (H₂O) in both solid and liquid forms.
  
  
• Option 3 is correct. Souring of milk is a chemical change because bacteria convert lactose into lactic acid, altering the milk’s chemical composition.
  
  

Thus, option (b) is the correct answer.

25. Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of: [UPSC CSE Pre. 2014]

(a) Algae and bacteria
 (b) Algae and fungi
 (c) Bacteria and fungi
 (d) Fungi and mosses

Solution: (b)
 Explanation:
 Lichens are a symbiotic association of algae and fungi:

• The algae (or cyanobacteria) produce food via photosynthesis.
  
  
• The fungi provide structure, protection, and moisture retention.
  
  

Lichens play a crucial role in pioneering ecological succession by breaking down rocks and forming soil, enabling plant growth in barren environments.

Thus, option (b) is the correct answer.

26. Which one of the following is the process involved in photosynthesis? [UPSC CSE Pre. 2014]

(a) Potential energy is released to form free energy
 (b) Free energy is converted into potential energy and stored
 (c) Food is oxidized to release carbon dioxide and water
 (d) Oxygen is taken in, and carbon dioxide and water vapor are given out

Solution: (b)
 Explanation:
 Photosynthesis is the process by which plants convert sunlight into chemical energy stored in glucose.

• Sunlight provides free energy, which plants store as potential energy in chemical bonds through the production of glucose.
  
  
• Option (a) is incorrect. Potential energy is stored, not released, in photosynthesis.
  
  
• Option (c) is incorrect. This describes respiration, not photosynthesis.
  
  
• Option (d) is incorrect. Plants take in CO₂ and release O₂ during photosynthesis, the opposite of what the option states.
  
  

Thus, option (b) is the correct answer.

27. Among the following organisms, which one does not belong to the class of the other three? [UPSC CSE Pre. 2014]

(a) Crab
 (b) Mite
 (c) Scorpion
 (d) Spider

Solution: (a)
 Explanation:

• Mite, Scorpion, and Spider belong to the class Arachnida, which are joint-legged invertebrates with eight legs.
  
  
• Crab, however, belongs to the class Crustacea, which is a different arthropod group.
  
  

Thus, option (a) is the correct answer.

28. Which of the following statements is/are correct regarding vegetative propagation of plants? [UPSC CSE Pre. 2014]

1. Vegetative propagation produces clonal populations.
   
   
2. Vegetative propagation helps in eliminating the virus.
   
   
3. Vegetative propagation can be practiced most of the year.
   
   

Select the correct answer using the code given below:
 (a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (c)
 Explanation:

• Statement 1 is correct. Vegetative propagation produces clonal populations, meaning all plants produced are genetically identical to the parent plant.
  
  
• Statement 2 is incorrect. Vegetative propagation does not eliminate viruses. In fact, viruses can be transmitted from the parent plant to the new plants through this method.
  
  
• Statement 3 is correct. Vegetative propagation can be practiced most of the year, but the success rate depends on the type of plant and environmental conditions.
  
  

Thus, option (c) is the correct answer.

Types of Vegetative Propagation:

• Stem cuttings – Used in plants like rose, hibiscus.
  
  
• Grafting – Common in mango, citrus plants.
  
  
• Layering – Used in jasmine, strawberry.
  
  
• Division – Used in tuberous plants like potatoes.
  
  

29. Fruits stored in a cold chamber exhibit longer storage life because: [UPSC CSE Pre. 2013]

(a) Exposure to sunlight is prevented
 (b) Concentration of carbon dioxide in the environment is increased
 (c) Rate of respiration is decreased
 (d) There is an increase in humidity

Solution: (c)
 Explanation:

• Fruits undergo respiration and transpiration, which lead to ripening and decay.
  
  
• Higher temperature increases respiration, shortening the fruit’s shelf life.
  
  
• Cold storage reduces the rate of respiration, thus slowing down decay and increasing the storage life of fruits.
  
  

Thus, option (c) is the correct answer.

30. Many transplanted seedlings do not grow because: [UPSC CSE Pre. 2013]

(a) The new soil does not contain favorable minerals
 (b) Most of the root hairs grip the new soil too hard
 (c) Most of the root hairs are lost during transplantation
 (d) Leaves get damaged during transplantation

Solution: (c)
 Explanation:

• Root hairs are responsible for absorbing water and nutrients.
  
  
• During transplantation, many root hairs are lost, leading to reduced water uptake and potential wilting.
  
  
• Other factors like soil quality and leaf damage may impact growth, but the main reason is the loss of root hairs.
  
  

Thus, option (c) is the correct answer.

31. Which of the following statements is/are correct? [UPSC CSE Pre. 2013]

1. Viruses lack enzymes necessary for the generation of energy.
   
   
2. Viruses can be cultured in any synthetic medium.
   
   
3. Viruses are transmitted from one organism to another by biological vectors only.
   
   

Select the correct answer using the code given below:
 (a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (a)
 Explanation:

• Statement 1 is correct. Viruses lack metabolic enzymes and cannot generate their own energy. They rely entirely on host cells for reproduction.
  
  
• Statement 2 is incorrect. Viruses cannot be cultured in synthetic media because they require a living host cell for replication.
  
  
• Statement 3 is incorrect. Viruses are transmitted by both biological vectors (e.g., mosquitoes, ticks) and mechanical vectors (e.g., contaminated surfaces, wind, water).
  
  

Thus, option (a) is the correct answer.

32. Ball bearings are used in bicycles, cars, etc., because: [UPSC CSE Pre. 2013]

(a) The actual area of contact between the wheel and axle is increased
 (b) The effective area of contact between the wheel and axle is increased
 (c) The effective area of contact between the wheel and axle is reduced
 (d) None of the above statements is correct

Solution: (c)
 Explanation:

• Ball bearings are rolling-element bearings that reduce friction and support loads in machines.
  
  
• They reduce the effective area of contact between moving parts, allowing smoother motion with less friction.
  
  
• By replacing sliding friction with rolling friction, they improve efficiency in bicycles, cars, and other machinery.
  
  

Thus, option (c) is the correct answer.

33. The known forces of nature can be divided into four classes: gravity, electromagnetism, weak nuclear force, and strong nuclear force. Which one of the following statements is not correct? [UPSC CSE Pre. 2013]

(a) Gravity is the strongest of the four
 (b) Electromagnetism acts only on particles with an electric charge
 (c) Weak nuclear force causes radioactivity
 (d) Strong nuclear force holds protons and neutrons inside the nucleus of an atom

Solution: (a)
 Explanation:

• The four fundamental forces in nature are:
  
  
  1. Gravitational Force – The weakest force but has an infinite range. It governs planetary motion.
     
     
  2. Electromagnetic Force – Affects charged particles and is responsible for electricity and magnetism.
     
     
  3. Weak Nuclear Force – Causes radioactive decay (beta decay).
     
     
  4. Strong Nuclear Force – The strongest force, responsible for holding protons and neutrons together inside an atomic nucleus.
     
     
• Gravity is actually the weakest force, not the strongest.
  
  

Thus, option (a) is incorrect, making it the correct answer.

34. Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? [UPSC CSE Pre. 2013]

1. Dispersion
   
   
2. Refraction
   
   
3. Internal reflection
   
   

Select the correct answer using the codes given below:

(a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:

• A rainbow is formed due to the combined effects of:
  
  
  1. Refraction – Light bends as it enters and exits the raindrop.
     
     
  2. Dispersion – Light splits into seven colors (VIBGYOR) due to different wavelengths bending at different angles.
     
     
  3. Total Internal Reflection – Some of the refracted light reflects inside the raindrop before exiting.
     
     

Thus, option (d) is the correct answer.

35. Consider the following phenomena: [UPSC CSE Pre. 2013]

1. Size of the sun at dusk
   
   
2. Color of the sun at dawn
   
   
3. Moon being visible at dawn
   
   
4. Twinkling of stars in the sky
   
   
5. Pole star being visible in the sky
   
   

Which of the above are optical illusions?

(a) 1, 2, and 3
 (b) 3, 4, and 5
 (c) 1, 2, and 4
 (d) 2, 3, and 5

Solution: (c)
 Explanation:

• Optical illusions occur due to atmospheric refraction or scattering of light.
  
  
• Statement 1 (Size of the sun at dusk) – Correct
  
  
  • The sun appears larger at sunrise and sunset due to atmospheric refraction bending its light.
    
    
• Statement 2 (Color of the sun at dawn) – Correct
  
  
  • The sun appears reddish at dawn due to Rayleigh scattering, which removes shorter wavelengths (blue and violet) from direct sunlight.
    
    
• Statement 3 (Moon being visible at dawn) – Incorrect
  
  
  • The moon is visible due to its orbit and position relative to the sun, not due to an optical illusion.
    
    
• Statement 4 (Twinkling of stars) – Correct
  
  
  • The twinkling of stars is caused by atmospheric refraction, where light bends continuously due to variations in air density.
    
    
• Statement 5 (Pole star visibility) – Incorrect
  
  
  • The Pole Star appears fixed because it aligns with Earth's rotational axis, not due to an optical illusion.
    
    

Thus, option (c) is the correct answer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

APPLIED SCIENCE

 

1. With reference to Radioisotope Thermoelectric Generators (RTGs), consider the following statements: (UPSC CSE Prelims 2024)

1. RTGs are miniature fission reactors.
   
   
2. RTGs are used for powering the onboard systems of spacecraft.
   
   
3. RTGs can use Plutonium-238, which is a by-product of weapons development.
   
   

Which of the statements given above are correct?

(a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Answer: (b) 2 and 3 only

Detailed Explanation:

• RTGs are not miniature fission reactors. They do not operate through controlled nuclear fission like a nuclear reactor; instead, they generate electricity through the natural radioactive decay of isotopes such as Plutonium-238. Hence, Statement 1 is incorrect.
  
  
• RTGs are used in space exploration, particularly in spacecraft like Voyager, Curiosity rover, and Perseverance rover, where solar power is not feasible due to distance from the Sun. Hence, Statement 2 is correct.
  
  
• Plutonium-238 is used in RTGs and is produced as a by-product of nuclear weapons programs. Hence, Statement 3 is correct.
  
  

Thus, the correct answer is (b) 2 and 3 only.

2. Which one of the following words/phrases is most appropriately used to denote "an interoperable network of 3D virtual worlds that can be accessed simultaneously by millions of users, who can exert property rights over virtual items"? (UPSC CSE Prelims 2024)

(a) Big data analytics
 (b) Cryptography
 (c) Metaverse
 (d) Virtual matrix

Answer: (c) Metaverse

Detailed Explanation:

• The Metaverse is a virtual reality-based interconnected digital space where users can interact in 3D virtual worlds, own digital assets, and engage in various activities using avatars.
  
  
• Big data analytics refers to the process of analyzing massive amounts of data.
  
  
• Cryptography is the science of securing communication through encryption techniques.
  
  
• Virtual matrix is not a recognized term in this context.
  
  

Thus, the correct answer is (c) Metaverse.

3. Consider the following statements: (UPSC CSE Prelims 2024)

Statement-I: Giant stars live much longer than dwarf stars.
 Statement-II: Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.

Which one of the following is correct in respect of the above statements?

(a) Both Statement-I and Statement-II are correct, and Statement-II explains Statement-I
 (b) Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
 (c) Statement-I is correct, but Statement-II is incorrect
 (d) Statement-I is incorrect, but Statement-II is correct

Answer: (d) Statement-I is incorrect, but Statement-II is correct

Detailed Explanation:

• Giant stars burn their fuel at a much higher rate than dwarf stars. As a result, their lifespan is much shorter compared to dwarf stars. For example, massive stars like supergiants burn out in millions of years, whereas dwarf stars like red dwarfs can last for billions of years. (Statement-I is incorrect).
  
  
• Giant stars undergo nuclear fusion at a much higher rate, leading to their rapid energy output and expansion. (Statement-II is correct).
  
  

Thus, the correct answer is (d) Statement-I is incorrect, but Statement-II is correct.

4. Consider the following activities: (UPSC CSE Prelims 2024)

1. Identification of narcotics on passengers at airports or in aircraft
   
   
2. Monitoring of precipitation
   
   
3. Tracking the migration of animals
   
   

In how many of the above activities can radars be used?

(a) Only one
 (b) Only two
 (c) All three
 (d) None

Answer: (b) Only two

Detailed Explanation:

• Radars are widely used for weather monitoring, including precipitation detection (such as Doppler radar used in meteorology). (Statement 2 is correct).
  
  
• Radars are used to track migratory birds and animals, particularly in conservation studies. (Statement 3 is correct).
  
  
• Radar is not typically used for narcotics detection; instead, X-ray scanners, ion mobility spectrometry, and sniffing dogs are used at airports. (Statement 1 is incorrect).
  
  

Thus, the correct answer is (b) Only two.

5. Consider the following aircraft: (UPSC CSE Prelims 2024)

1. Rafael
   
   
2. MiG-29
   
   
3. Tejas MK-1
   
   

How many of the above are considered fifth-generation fighter aircraft?

(a) Only one
 (b) Only two
 (c) All three
 (d) None

Answer: (d) None

Detailed Explanation:

• Fifth-generation fighter aircraft have characteristics such as stealth technology, advanced avionics, supercruise capability, and network-centric warfare.
  
  
• Rafale is a 5-generation aircraft with some stealth features.
  
  
• MiG-29 is a 4th-generation aircraft, designed during the Cold War.
  
  
• Tejas MK-1 is a 4th-generation fighter developed by India.
  
  

Since none of these aircraft belong to the fifth generation, the correct answer is (d) None.

6. In which of the following are hydrogels used? (UPSC CSE Prelims 2024)

1. Controlled drug delivery in patients
   
   
2. Mobile air-conditioning systems
   
   
3. Preparation of industrial lubricants
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 1 and 2 only
 (c) 2 and 3 only
 (d) 1, 2 and 3

Answer: (d) 1, 2 and 3

Detailed Explanation:

• Hydrogels are extensively used in medicine for controlled drug delivery, as they have high water content and can gradually release medication. (Statement 1 is correct).
  
  
• Hydrogels are used in cooling systems, especially in mobile air-conditioning as they can store and release water efficiently. (Statement 2 is correct).
  
  
• Hydrogels are also used in industrial lubricants, as they reduce friction in machinery. (Statement 3 is correct).
  
  

Thus, the correct answer is (d) 1, 2 and 3.

 

 

1. 'Wolbachia method' is sometimes talked about with reference to which one of the following? [UPSC CSE Pre 2023]

(a) Controlling the viral diseases spread by mosquitoes.
 (b) Converting crop residues into packing material.
 (c) Producing biodegradable plastics.
 (d) Producing biochar from thermochemical conversion of biomass.

Solution: (a)
 Explanation:

• The Wolbachia method is a biological control strategy used to curb the spread of mosquito-borne viral diseases like dengue, Zika, and chikungunya.
  
  
• Wolbachia is a type of bacterium that, when introduced into mosquitoes, reduces their ability to transmit these viruses.
  
  
• When Wolbachia-infected mosquitoes mate with non-infected ones, the resulting eggs either do not hatch or produce mosquitoes that also carry Wolbachia, disrupting the transmission cycle.
  
  

Thus, option (a) is the correct answer.

2. Aerial metagenomics best refers to which one of the following situations? [UPSC CSE Pre 2023]

(a) Collecting DNA samples from air in a habitat at one go.
 (b) Understanding the genetic makeup of avian species of a habitat.
 (c) Using air-borne devices to collect blood samples from moving animals.
 (d) Sending drones to inaccessible areas to collect plant and animal samples from land surfaces and water bodies.

Solution: (a)
 Explanation:

• Aerial metagenomics is the process of collecting and analyzing DNA samples present in air to study the genetic material of microorganisms, including bacteria, viruses, and fungi.
  
  
• This method allows scientists to study airborne microbes, track pathogen movement, and monitor biodiversity in an ecosystem.
  
  

Thus, option (a) is the correct answer.

3. 'Microsatellite DNA' is used in the case of which one of the following? [UPSC CSE Pre 2023]

(a) Studying evolutionary relationships among various species of fauna.
 (b) Stimulating stem cells to transform into diverse functional tissues.
 (c) Promoting clonal propagation of horticultural plants.
 (d) Assessing the efficacy of drugs by conducting a series of drug trials in a population.

Solution: (a)
 Explanation:

• Microsatellite DNA, also known as short tandem repeats (STRs), consists of repeating sequences of DNA.
  
  
• These highly polymorphic markers are useful in population genetics and phylogenetic studies, allowing scientists to determine evolutionary relationships among species.
  
  
• By analyzing microsatellite variations, researchers can assess genetic diversity, ancestry, and migration patterns of species.
  
  

Thus, option (a) is the correct answer.

4. Consider the following statements: [UPSC CSE Pre 2023]

1. Carbon fibres are used in the manufacture of components used in automobiles and aircraft.
   
   
2. Carbon fibres, once used, cannot be recycled.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (a)
 Explanation:

• Statement 1 is correct:
  
  
  • Carbon fibre is lightweight yet strong, making it an essential material in the automobile and aerospace industries.
    
    
  • It enhances fuel efficiency and structural integrity.
    
    
• Statement 2 is incorrect:
  
  
  • Carbon fibre can be recycled, although the process is challenging.
    
    
  • Recycled carbon fibre is often used in sports equipment (e.g., tennis rackets, golf clubs) and other applications requiring lightweight materials.
    
    

Thus, option (a) is the correct answer.

5. Consider the following actions: [UPSC CSE Pre 2023]

1. Detection of a car crash/collision resulting in the deployment of airbags almost instantaneously.
   
   
2. Detection of the accidental free fall of a laptop towards the ground, leading to the immediate turning off of the hard drive.
   
   
3. Detection of the tilt of a smartphone, resulting in the rotation of display between portrait and landscape mode.
   
   

In how many of the above actions is the function of an accelerometer required?

(a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (c)
 Explanation:
 An accelerometer is a device that measures acceleration, vibration, and motion. It converts mechanical movement into electrical signals.

• Statement 1 is correct:
  
  
  • In car crash detection systems, accelerometers detect sudden deceleration and trigger airbag deployment.
    
    
• Statement 2 is correct:
  
  
  • In laptops, accelerometers detect sudden drops and turn off hard drives to prevent damage.
    
    
• Statement 3 is correct:
  
  
  • In smartphones, accelerometers detect tilt and adjust the screen between portrait and landscape modes.
    
    

Since all three actions rely on accelerometers, option (c) is the correct answer.

6. 
   With reference to the role of biofilters in a Recirculating Aquaculture System, consider the following statements:

1. Biofilters provide waste treatment by removing uneaten fish feed.
   
   
2. Biofilters convert ammonia present in fish waste into nitrate.
   
   
3. Biofilters increase phosphorus as a nutrient for fish in water.
   
   

How many of the above statements are correct? [UPSC CSE Pre 2023]
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (b)
 Explanation:

• Statement 1 is incorrect: Biofilters do not remove uneaten fish feed directly. Uneaten feed and fish waste are removed through mechanical filtration before biofilters handle dissolved waste.
  
  
• Statement 2 is correct: Biofilters host nitrifying bacteria that convert toxic ammonia from fish waste into less harmful nitrate through a two-step biological process.
  
  
• Statement 3 is incorrect: Biofilters do not increase phosphorus. Instead, they help remove phosphorus from the water, preventing excessive nutrient buildup.
  
  

Thus, only two statements are correct.

7. Consider the following pairs:

Objects in space	Description
1. Cepheids	Giant clouds of dust and gas in space
2. Nebulae	Stars that brighten and dim periodically
3. Pulsars	Neutron stars formed when massive stars run out of fuel and collapse

How many of the above pairs are correctly matched? [UPSC CSE Pre 2023]
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (a)
 Explanation:

• Pair 1 is incorrect: Cepheids are not giant clouds of dust and gas but are a type of variable star that brightens and dims periodically. They are used as standard candles in astronomy to measure distances.
  
  
• Pair 2 is incorrect: Nebulae are clouds of gas and dust in space, not stars that brighten and dim. Some nebulae are regions where new stars are forming, while others are remnants of dying stars.
  
  
• Pair 3 is correct: Pulsars are highly magnetized neutron stars that emit beams of electromagnetic radiation. They are formed when massive stars collapse at the end of their life cycle.
  
  

Thus, only one pair is correctly matched.

8. Which one of the following countries has its own Satellite Navigation System? [UPSC CSE Pre 2023]

(a) Australia
 (b) Canada
 (c) Israel
 (d) Japan

Solution: (d)
 Explanation:

• Japan operates the Quasi-Zenith Satellite System (QZSS), a regional satellite navigation system that enhances GPS coverage, particularly in East Asia and Oceania.
  
  
• Australia, Canada, and Israel do not have independent satellite navigation systems but rely on global systems like GPS (USA), Galileo (EU), or GLONASS (Russia).
  
  

Thus, Japan is the correct answer.

9. Consider the following statements:

1. Ballistic missiles are jet-propelled at subsonic speeds throughout their flights, while cruise missiles are rocket-powered only in the initial phase of flight.
   
   
2. Agni-V is a medium-range supersonic cruise missile, while BrahMos is a solid-fuelled intercontinental ballistic missile.
   
   

Which of the statements given above is/are correct? [UPSC CSE Pre 2023]
 (a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (d)
 Explanation:

• Statement 1 is incorrect: Cruise missiles are jet-powered and travel at subsonic or supersonic speeds throughout their flight, while ballistic missiles are rocket-powered only in the initial phase and then follow a free-fall trajectory.
  
  
• Statement 2 is incorrect: Agni-V is an intercontinental ballistic missile (ICBM), not a cruise missile. BrahMos is a supersonic cruise missile, not an ICBM.
  
  

Thus, neither of the statements is correct.

10. With reference to "Software as a Service (SaaS)", consider the following statements:

1. SaaS buyers can customize the user interface and change data fields.
   
   
2. SaaS users can access their data through their mobile devices.
   
   
3. Outlook, Hotmail, and Yahoo! Mail are forms of SaaS.
   
   

Which of the statements given above are correct? [UPSC CSE Pre 2022]
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:

• Statement 1 is correct: Many SaaS applications allow users to customize their interface, data fields, and workflows to fit their needs.
  
  
• Statement 2 is correct: SaaS applications are cloud-based, meaning users can access their data from any internet-connected device, including mobile phones.
  
  
• Statement 3 is correct: Email services like Outlook, Hotmail, and Yahoo! Mail are classic examples of SaaS, where users access the software through a web browser without installing it on their devices.
  
  

Thus, all three statements are correct.

11. Consider the following technologies:

1. Closed-Circuit Television (CCTV)
   
   
2. Radio Frequency Identification (RFID)
   
   
3. Wireless Local Area Network (WLAN)
   
   

Which of the above are considered short-range communication technologies? [UPSC CSE Pre 2022]
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:

• CCTV (Closed-Circuit Television): Uses wired or wireless short-range transmission for video surveillance.
  
  
• RFID (Radio Frequency Identification): A short-range communication technology used in tracking, inventory management, and contactless payments.
  
  
• WLAN (Wireless Local Area Network): Covers short distances, typically within homes, offices, or campuses, and enables wireless communication over limited areas.
  
  

Thus, all three technologies are considered short-range communication technologies.

12. Consider the following statements:
13. Biofilms can form on medical implants within human tissues.
14. Biofilms can form on food and food processing surfaces.
15. Biofilms can exhibit antibiotic resistance.

Which of the statements given above are correct? [UPSC CSE Pre 2022]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (d)
Explanation:

• Statement 1 is correct: Biofilms can develop on medical implants, such as catheters, pacemakers, and prosthetic joints. These microbial communities adhere to surfaces and are encased in a self-produced extracellular matrix, making them difficult to eliminate.
• Statement 2 is correct: Biofilms can form on food and food processing surfaces, leading to contamination. Pathogens like Escherichia coli and Salmonella enterica thrive in biofilms, posing significant food safety risks.
• Statement 3 is correct: Biofilms exhibit increased antibiotic resistance due to their protective matrix and altered microbial physiology. This resistance complicates treatment and can contribute to chronic infections.

Thus, all three statements are correct.

13. In the context of vaccines manufactured to prevent the COVID-19 pandemic, consider the following statements:
14. The Serum Institute of India produced a COVID-19 vaccine named Covishield using the mRNA platform.
15. Sputnik V vaccine is manufactured using a vector-based platform.
16. COVAXIN is an inactivated pathogen-based vaccine.

Which of the statements given above are correct? [UPSC CSE Pre 2022]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Solution: (b)
Explanation:

• Statement 1 is incorrect: Covishield, produced by the Serum Institute of India, was developed using a viral vector platform, not an mRNA platform. It is based on a modified chimpanzee adenovirus (ChAdOx1) carrying the spike protein of SARS-CoV-2.
• Statement 2 is correct: Sputnik V is a vector-based vaccine. It uses two different adenoviruses (Ad26 and Ad5) as carriers for the SARS-CoV-2 spike protein to stimulate an immune response.
• Statement 3 is correct: Covaxin, developed by Bharat Biotech, is an inactivated whole-virus vaccine. It contains a chemically inactivated form of SARS-CoV-2, which cannot replicate but still triggers an immune response.

Thus, only statements 2 and 3 are correct.

14. If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth?
15. GPS and navigation systems could fail.
16. Tsunamis could occur at equatorial regions.
17. Power grids could be damaged.
18. Intense auroras could occur over much of the Earth.
19. Forest fires could take place over much of the planet.
20. Orbits of the satellites could be disturbed.
21. Shortwave radio communication of the aircraft flying over polar regions could be interrupted.

Select the correct answer using the code given below: [UPSC CSE Pre 2022]
(a) 1, 2, 4 and 5 only
(b) 2, 3, 5, 6 and 7 only
(c) 1, 3, 4, 6 and 7 only
(d) 1, 2, 3, 4, 5, 6 and 7

Solution: (c)
Explanation:

• Statement 1 is correct: Solar flares can disrupt GPS and navigation systems by interfering with satellite signals and ionospheric conditions.
• Statement 2 is incorrect: Solar storms do not cause tsunamis. Tsunamis are triggered by underwater seismic activity, such as earthquakes and volcanic eruptions, not solar radiation.
• Statement 3 is correct: Power grids can be damaged due to induced geomagnetic currents, leading to transformer failures and widespread blackouts.
• Statement 4 is correct: Intense solar storms can cause auroras to appear at lower latitudes than usual, creating dazzling light displays.
• Statement 5 is incorrect: Solar storms do not directly cause forest fires. While they emit radiation, they do not generate enough heat to ignite vegetation.
• Statement 6 is correct: Solar storms can alter satellite orbits by heating the Earth's upper atmosphere, increasing atmospheric drag and causing satellites to descend.
• Statement 7 is correct: Shortwave radio communication, particularly for aircraft flying over polar regions, can be interrupted due to ionospheric disturbances caused by solar flares.

Thus, the correct answer includes statements 1, 3, 4, 6, and 7.

15. With reference to Non-Fungible Tokens (NFTs), consider the following statements:

1. They enable the digital representation of physical assets.
   
   
2. They are unique cryptographic tokens that exist on a blockchain.
   
   
3. They can be traded or exchanged at equivalency and therefore can be used as a medium of commercial transactions.
   
   

Which of the statements given above are correct? [UPSC CSE Pre 2022]
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (a)

Explanation:

• Statement 1 is correct: NFTs enable the digital representation of physical assets such as art, videos, music, and more. Anything that can be converted into a digital form can be an NFT.
  
  
• Statement 2 is correct: NFTs are cryptographic assets that exist on a blockchain with unique identification codes and metadata, making them distinguishable from each other.
  
  
• Statement 3 is incorrect: Unlike cryptocurrencies, NFTs cannot be exchanged at equivalency because each NFT is unique. Fungible tokens like cryptocurrencies can be traded equivalently, but NFTs represent distinct digital assets.
  
  

16. Consider the following statements regarding DNA Barcoding:

DNA Barcoding can be a tool to:

1. Assess the age of a plant or animal.
   
   
2. Distinguish among species that look alike.
   
   
3. Identify undesirable animal or plant materials in processed foods.
   
   

Which of the statements given above is/are correct? [UPSC CSE Pre 2022]
 (a) 1 only
 (b) 3 only
 (c) 1 and 2 only
 (d) 2 and 3 only

Solution: (d)

Explanation:

• Statement 1 is incorrect: The age of plants or animals is determined using radiometric dating techniques such as Carbon-14 dating, not DNA barcoding.
  
  
• Statement 2 is correct: DNA barcoding helps distinguish species, even when they look similar, by using genetic markers unique to each species.
  
  
• Statement 3 is correct: DNA barcoding is used in the food industry to detect undesirable animal or plant materials in processed foods, ensuring food authenticity and preventing fraud.
  
  

17. Which one of the following is the context in which the term 'Qubit' is mentioned? [UPSC CSE Pre 2022]

(a) Cloud Services
 (b) Quantum Computing
 (c) Visible Light Communication Technologies
 (d) Wireless Communication Technologies

Solution: (b)

Explanation:

• A qubit (quantum bit) is the fundamental unit of quantum information in quantum computing.
  
  
• Unlike classical bits (which store either 0 or 1), qubits can exist in multiple states simultaneously due to the principles of superposition and entanglement, making quantum computers more powerful than classical ones.
  
  
• Quantum computing has applications in fields like cryptography, medicine, artificial intelligence, and physics.
  
  

18. Consider the following:

1. Aarogya Setu
   
   
2. CoWIN
   
   
3. DigiLocker
   
   
4. DIKSHA
   
   

Which of the above are built on top of open-source digital platforms? [UPSC CSE Pre 2022]
 (a) 1 and 2 only
 (b) 2, 3 and 4 only
 (c) 1, 3 and 4 only
 (d) 1, 2, 3 and 4

Solution: (d)

Explanation:

• All four platforms are built on open-source digital technologies.
  
  
  • Aarogya Setu was developed using open-source technologies as per the MeitY Open-Source Policy.
    
    
  • CoWIN is built on Sunbird ED, an open-source software framework under the MIT license.
    
    
  • DigiLocker follows MeitY’s open-source policy.
    
    
  • DIKSHA is also based on Sunbird ED, supporting educational content.
    
    

19. With reference to Web 3.0, consider the following statements:

1. Web 3.0 technology enables people to control their own data.
   
   
2. In a Web 3.0 world, there can be blockchain-based social networks.
   
   
3. Web 3.0 is operated by users collectively rather than a corporation.
   
   

Which of the statements given above are correct? [UPSC CSE Pre 2022]
 (a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2 and 3

Solution: (d)

Explanation:

• Statement 1 is correct: Web 3.0 is a decentralized internet model where users have greater control over their data, unlike Web 2.0, where companies control user data.
  
  
• Statement 2 is correct: Blockchain-based applications, including decentralized social networks, are possible under Web 3.0.
  
  
• Statement 3 is correct: Instead of being controlled by corporations, Web 3.0 operates on decentralized technologies, allowing collective user ownership and governance.

20. Which one of the following statements best reflects the idea behind the 'Fractional Orbital Bombardment System' often talked about in media? [UPSC CSE Pre 2022]

(a) A hypersonic missile is launched into space to counter the asteroid approaching the Earth and explode it in space.
 (b) A spacecraft lands on another planet after making several orbital motions.
 (c) A missile is put into a stable orbit around the Earth and deorbits over a target on the Earth.
 (d) A spacecraft moves along a comet with the same speed and places a probe on its surface.

Solution: (c)

Explanation:

• A Fractional Orbital Bombardment System (FOBS) is a warhead delivery system that places a missile into a low Earth orbit before deorbiting it to strike its target.
  
  
• Developed by the Soviet Union in the 1960s, it was one of the earliest attempts to use space-based nuclear weapons delivery.
  
  
• In August 2021, China tested a weapon that combined FOBS with a hypersonic glide vehicle.
  
  

Advantages and Disadvantages of FOBS:

Advantage	Disadvantage
No range limit	Complex to develop and deploy
Flight path does not reveal target location	Vulnerable to anti-satellite weapons
Can evade NORAD’s north-facing early warning systems by approaching over the South Pole	Violates the Outer Space Treaty, which prohibits placing weapons of mass destruction in orbit

What is a retrograde engine burn?

• A retrograde engine burn is when a spacecraft fires its engines to slow down and move in the opposite direction.
  
  
• Used for orbital entry, spacecraft rendezvous, or deorbiting.
  
  
• Example: The Apollo missions used retrograde burns to enter lunar orbit and return to Earth.
  
  

21. Consider the following statements: [UPSC CSE Pre 2022]

1. Other than those made by humans, nanoparticles do not exist in nature.
   
   
2. Nanoparticles of some metallic oxides are used in the manufacture of some cosmetics.
   
   
3. Nanoparticles of some commercial products which enter the environment are unsafe for humans.
   
   

Which of the statements given above is/are correct?
 (a) 1 only
 (b) 3 only
 (c) 1 and 2 only
 (d) 2 and 3 only

Solution: (d)

Explanation:

• Statement 1 is incorrect: Nanoparticles exist naturally in volcanic ash, forest fire smoke, sea spray, and erosion processes. They are not solely human-made.
  
  
• Statement 2 is correct: Metallic oxide nanoparticles, such as titanium dioxide and zinc oxide, are used in cosmetics like sunscreens for UV protection.
  
  
• Statement 3 is correct: Some nanoparticles from commercial products pose health risks. For example, diesel exhaust nanoparticles are linked to respiratory issues and environmental contamination.
  
  

How do nanoparticles enter the food chain?

1. Through plants: Absorbed by roots or leaves if present in soil or water.
   
   
2. Through animals: Grazing animals ingest nanoparticles from contaminated plants or water.
   
   
3. Through food processing: Nanoparticles can be introduced via food packaging or additives.
   
   

22. Which one of the following statements best describes the 'Polar Code'? [UPSC CSE Pre 2022]

(a) It is the international code of safety for ships operating in polar waters.
 (b) It is the agreement of the countries around the North Pole regarding the demarcation of their territories in the polar region.
 (c) It is a set of norms to be followed by the countries whose scientists undertake research studies in the North Pole and South Pole.
 (d) It is a trade and security agreement between the member countries of the Arctic Council.

Solution: (a)

Explanation:

• The Polar Code is an international regulation for the safety and environmental protection of ships operating in Arctic and Antarctic waters.
  
  
• Adopted by the International Maritime Organization (IMO) in 2014, it came into force in 2017.
  
  
• The increase in maritime activities due to climate change and new shipping routes led to the development of this code.
  
  

23. With reference to polyethylene terephthalate, the use of which is so widespread in our daily lives, consider the following statements: [UPSC CSE Pre 2022]

1. Its fibers can be blended with wool and cotton fibers to reinforce their properties.
   
   
2. Containers made of it can be used to store any alcoholic beverage.
   
   
3. Bottles made of it can be recycled into other products.
   
   
4. Articles made of it can be easily disposed of by incineration without causing greenhouse gas emissions.
   
   

Which of the statements given above are correct?
 (a) 1 and 3 only
 (b) 2 and 4 only
 (c) 1 and 4 only
 (d) 2 and 3 only

Solution: (a)

Explanation:

• Statement 1 is correct: PET fibers can be blended with wool and cotton to enhance their properties. Example: Terylene, a polyester fiber made from PET, is commonly blended with cotton or wool.
  
  
• Statement 2 is incorrect: PET containers cannot be used to store alcoholic beverages as PET degrades in the presence of ethanol over time. It is mainly used for water, soft drinks, juices, and edible oils.
  
  
• Statement 3 is correct: PET bottles can be recycled into fibers, carpets, clothing, furniture, and engineering plastics. PET recycling is well-established, reducing waste and conserving resources.
  
  
• Statement 4 is incorrect: Incineration of PET releases greenhouse gases, primarily carbon dioxide and water vapor. It may also release toxic substances like dioxins and furans.
  
  

24. In the context of hereditary diseases, consider the following statements: [UPSC CSE Pre 2021]

1. Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of the egg.
   
   
2. A child inherits mitochondrial diseases entirely from the mother and not from the father.
   
   

Which of the statements given above is/are correct?
 (a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (c)

Explanation:

• Statement 1 is correct: Mitochondrial replacement therapy (MRT) is an assisted reproductive technology that replaces faulty mitochondrial DNA with healthy mitochondrial DNA from a donor. It can be done before or after in vitro fertilization (IVF) using techniques such as:
  
  
  • Spindle Transfer (ST) – before fertilization
    
    
  • Pronuclear Transfer (PNT) – after fertilization
    
    
  • Polar Body Transfer (PBT) – alternative method
    
    
• Statement 2 is correct: Mitochondria have their own DNA (mtDNA), which is inherited only from the mother. The sperm contributes little or no mitochondria, meaning mitochondrial diseases are maternally inherited.
  
  

Important Tip:

• In Pronuclear Transfer (PNT), the mother’s fertilized egg’s nucleus is transferred into a donor egg, which has healthy mitochondria but its nucleus removed. The resulting zygote is implanted into the mother’s uterus.
  
  

25. Bollgard I and Bollgard II technologies are mentioned in the context of: [UPSC CSE Pre 2021]

(a) Clonal propagation of crop plants
 (b) Developing genetically modified crop plants
 (c) Production of plant growth substances
 (d) Production of biofertilizers

Solution: (b)

Explanation:

• Bollgard I and Bollgard II are genetically modified (GM) cotton varieties designed to provide protection against bollworm infestations.
  
  
• They contain an insecticidal protein from Bacillus thuringiensis (Bt), a naturally occurring soil bacterium.
  
  
• Bollgard I (Single-Gene Technology): Approved for commercialization in India in 2002.
  
  
• Bollgard II (Double-Gene Technology): Contains Cry1Ac and Cry2Ab genes, providing enhanced resistance against bollworms and Spodoptera caterpillar.
  
  

26. With reference to street lighting, how do sodium lamps differ from LED lamps? [UPSC CSE Pre 2021]

1. Sodium lamps produce light in 360 degrees, but it is not so in the case of LED lamps.
   
   
2. As streetlights, sodium lamps have a longer lifespan than LED lamps.
   
   
3. The spectrum of visible light from sodium lamps is almost monochromatic, while LED lamps offer significant color advantages in street lighting.
   
   

Select the correct answer using the code given below:
 (a) 3 only
 (b) 2 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (c)

Explanation:

• Statement 1 is correct: Sodium lamps emit light in 360 degrees, whereas LED lamps have a 180-degree beam angle, allowing for more focused lighting.
  
  
• Statement 2 is incorrect: Sodium lamps have a shorter lifespan than LED lamps.
  
  
  • High-Pressure Sodium (HPS) lamps last around 24,000 hours.
    
    
  • LED lamps last between 25,000 and 200,000 hours.
    
    
• Statement 3 is correct: Sodium lamps emit a nearly monochromatic yellow-orange light, making them less effective for color differentiation.
  
  
  • LED lamps offer a broader spectrum of light colors, providing better visibility and energy efficiency.

27. The term 'ACE2' is discussed in the context of:

[UPSC CSE Prelims 2021]
 (a) Genes introduced in genetically modified plants
 (b) Development of India's own satellite navigation system
 (c) Radio collars for wildlife tracking
 (d) Spread of viral diseases

Solution: (d)
 Explanation:
 Angiotensin-converting enzyme 2 (ACE2) is a protein found on the surface of various human cells, including those in the lungs, heart, kidneys, and intestines. It plays a crucial role in regulating functions such as blood pressure, wound healing, and inflammation. Importantly, ACE2 serves as the receptor that enables the SARS-CoV-2 virus, responsible for COVID-19, to enter and infect human cells. Hence, ACE2 is discussed in the context of viral disease spread.

28. Consider the following statements regarding viruses:

[UPSC CSE Prelims 2021]

1. Adenoviruses have single-stranded DNA genomes, whereas retroviruses have double-stranded DNA genomes.
   
   
2. The common cold is sometimes caused by an adenovirus, whereas AIDS is caused by a retrovirus.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (b)
 Explanation:

• Statement 1 is incorrect: Adenoviruses actually have double-stranded DNA genomes, not single-stranded. Retroviruses, on the other hand, have single-stranded RNA
  
  
• Statement 2 is correct: The common cold can sometimes be caused by adenoviruses. AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus.
  
  

Thus, only statement 2 is correct.

29. Regarding Recombinant Vector Vaccines, consider the following statements:

[UPSC CSE Prelims 2021]

1. Genetic engineering is applied in the development of these vaccines.
   
   
2. Bacteria and viruses are used as vectors.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (c)
 Explanation:

• Statement 1 is correct: Recombinant vector vaccines are developed using genetic engineering techniques. Scientists modify genetic material (DNA or RNA) and introduce it into host organisms to induce an immune response. Techniques such as DNA recombination, gene cloning, and gene transfer are used in this process.
  
  
• Statement 2 is correct: Both bacteria and viruses can act as vectors in recombinant vector vaccines. Examples include:
  
  
  • Bacterial vector vaccines: The BCG vaccine (for tuberculosis) and cholera vaccine.
    
    
  • Viral vector vaccines: The MMR (Measles, Mumps, and Rubella) vaccine and the HPV (Human Papillomavirus) vaccine.
    
    

Thus, both statements 1 and 2 are correct.

30. With reference to Visible Light Communication (VLC) technology, which of the following statements are correct?

[UPSC CSE Prelims 2020]

1. VLC uses electromagnetic spectrum wavelengths ranging from 375 to 780 nm.
   
   
2. VLC is known as long-range optical wireless communication.
   
   
3. VLC can transmit large amounts of data faster than Bluetooth.
   
   
4. VLC has no electromagnetic interference.
   
   

Select the correct answer using the code given below:

(a) 1, 2, and 3 only
 (b) 1, 2, and 4 only
 (c) 1, 3, and 4 only
 (d) 2, 3, and 4 only

Solution: (c)
 Explanation:

• Statement 1 is correct: VLC operates within the visible light spectrum, which has wavelengths between 375 to 780 nm in the electromagnetic spectrum.
  
  
• Statement 2 is incorrect: VLC is a short-range communication technology primarily used indoors. Long-range optical wireless communication usually refers to Free-Space Optical Communication (FSO), which uses infrared or near-infrared light.
  
  
• Statement 3 is correct: VLC can transmit data faster than Bluetooth, achieving speeds up to 500 Mbps or more using LEDs and even higher with laser-based systems. Bluetooth, in comparison, has a maximum data transfer rate of around 50 Mbps.
  
  
• Statement 4 is correct: VLC does not cause electromagnetic interference because it operates in the visible light spectrum rather than using radio waves, which are susceptible to interference.
  
  

Thus, the correct answer is (c) 1, 3, and 4 only.

31. With the present state of development, Artificial Intelligence (AI) can effectively do which of the following?

[UPSC CSE Prelims 2020]

1. Reduce electricity consumption in industrial units
   
   
2. Create meaningful short stories and songs
   
   
3. Assist in disease diagnosis
   
   
4. Perform text-to-speech conversion
   
   
5. Enable wireless transmission of electrical energy
   
   

Select the correct answer using the code given below:

(a) 1, 2, 3, and 5 only
 (b) 1, 3, and 4 only
 (c) 2, 4, and 5 only
 (d) 1, 2, 3, 4, and 5

Solution: (b)
 Explanation:

• AI can effectively perform the following tasks:
  
  
  • (1) Reduce electricity consumption in industrial units: AI-based energy management systems optimize power consumption using predictive analytics and smart sensors.
    
    
  • (3) Assist in disease diagnosis: AI can analyze medical images, lab reports, and patient histories to assist in identifying diseases.
    
    
  • (4) Perform text-to-speech conversion: AI-powered Natural Language Processing (NLP) and deep learning models enable high-quality speech synthesis.
    
    
• AI is not yet fully effective in the following tasks:
  
  
  • (2) Creating meaningful short stories and songs: AI can generate creative content, but it often lacks emotional depth and originality.
    
    
  • (5) Wireless transmission of electrical energy: This is a physical phenomenon that relies on electromagnetic waves, antennas, and wireless power transfer technology, not AI.
    
    

Thus, the correct answer is (b) 1, 3, and 4 only.

32. In India, the term 'Public Key Infrastructure' (PKI) is used in the context of:

[UPSC CSE Prelims 2020]

(a) Digital security infrastructure
 (b) Food security infrastructure
 (c) Healthcare and education infrastructure
 (d) Telecommunication and transportation infrastructure

Solution: (a)
 Explanation:
 Public Key Infrastructure (PKI) is a digital security framework that facilitates encryption, authentication, and secure communication over the internet. It uses public and private key cryptography to ensure data security, particularly in online transactions, e-governance, and digital signatures.

Thus, PKI is related to digital security infrastructure.

33. With reference to Blockchain Technology, consider the following statements:

[UPSC CSE Prelims 2020]

1. It is a public ledger that everyone can inspect, but which no single user controls.
   
   
2. The structure and design of blockchain ensure that all the data stored in it is exclusively about cryptocurrency.
   
   
3. Applications based on blockchain technology can be developed without requiring permission from any central authority.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 1 and 2 only
 (c) 2 only
 (d) 1 and 3 only

Solution: (d)
 Explanation:

• Statement 1 is correct: Blockchain is a decentralized, distributed ledger where transactions are recorded and validated without central authority control. Anyone can inspect the data, but no single entity has control over the entire blockchain.
  
  
• Statement 2 is incorrect: Blockchain is not limited to cryptocurrency. While it was initially developed for Bitcoin, it is now widely used in supply chain management, digital identity verification, smart contracts, and secure voting systems.
  
  
• Statement 3 is correct: Permissionless blockchains (such as Bitcoin and Ethereum) allow developers to create applications without requiring approval from a central authority.
  
  

Thus, the correct answer is (d) 1 and 3 only.

34. In India, under cyber insurance for individuals, which of the following benefits are generally covered, in addition to payment for the loss of funds and other benefits?

[UPSC CSE Prelims 2020]

1. Cost of restoration of the computer system in case of malware disrupting access to one's computer
   
   
2. Cost of a new computer if some miscreant willfully damages it, if proved so
   
   
3. Cost of hiring a specialized consultant to minimize the loss in case of cyber extortion
   
   
4. Cost of defense in the Court of Law if any third party files a suit
   
   

Select the correct answer using the code given below:

(a) 1, 2, and 4 only
 (b) 1, 3, and 4 only
 (c) 2 and 3 only
 (d) 1, 2, 3, and 4

Solution: (b)
 Explanation:
 Cyber insurance for individuals in India generally provides coverage for the following:

• Statement 1 is correct: The cost of restoring a computer system in case of malware attacks or data corruption is covered under cyber insurance. This includes data recovery and reinstallation of software.
  
  
• Statement 2 is incorrect: Cyber insurance does not cover the cost of a new computer in case of physical damage, even if it is caused by cybercrime. The insurance focuses on cyber-related risks, not hardware damage.
  
  
• Statement 3 is correct: Cyber insurance covers the cost of hiring a cybersecurity consultant to minimize financial or reputational losses in case of cyber extortion or ransomware attacks.
  
  
• Statement 4 is correct: Legal expenses incurred in defending a lawsuit filed by a third party due to cyber incidents (e.g., data breach, identity theft, or defamation) are covered under cyber insurance.
  
  

Thus, the correct answer is (b) 1, 3, and 4 only.

35. "The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometers long, with lasers shining between the craft." The experiment in question refers to:

[UPSC CSE Prelims 2020]

(a) Voyager-2
 (b) New Horizons
 (c) LISA Pathfinder
 (d) Evolved LISA

Solution: (d)
 Explanation:
 The experiment described refers to the Evolved Laser Interferometer Space Antenna (eLISA), a space-based gravitational wave detector.

• Evolved LISA (eLISA) is an advanced version of the Laser Interferometer Space Antenna (LISA)
  
  
• It consists of three spacecraft arranged in an equilateral triangle, with each side measuring about 1 million kilometers.
  
  
• Lasers are used to measure tiny changes in distance between the spacecraft, allowing scientists to detect gravitational waves emitted by black holes, neutron stars, and other cosmic events.
  
  
• This mission is led by the European Space Agency (ESA) and aims to explore the nature of black holes and gravitational waves in deep space.
  
  

Thus, the correct answer is (d) Evolved LISA.

36. With reference to carbon nanotubes, consider the following statements:

[UPSC CSE Prelims 2020]

1. They can be used as carriers of drugs and antigens in the human body.
   
   
2. They can be made into artificial blood capillaries for an injured part of the human body.
   
   
3. They can be used in biochemical sensors.
   
   
4. Carbon nanotubes are biodegradable.
   
   

Select the correct answer using the code given below:

(a) 1 and 2 only
 (b) 2, 3, and 4 only
 (c) 1, 3, and 4 only
 (d) 1, 2, 3, and 4

Solution: (c)
 Explanation:

• Statement 1 is correct: Carbon nanotubes (CNTs) can be used as carriers of drugs and antigens because of their large surface area, high penetration ability, and compatibility with biological systems. They can effectively target specific cells or tissues, making them useful for drug delivery in cancer treatment and vaccine development.
  
  
• Statement 2 is incorrect: While research is ongoing, carbon nanotubes are not yet blood-compatible. They can trigger blood clot formation, which can cause serious health risks. This makes them unsuitable for artificial blood capillaries.
  
  
• Statement 3 is correct: Carbon nanotubes are highly sensitive to changes in their environment, making them excellent materials for biochemical sensors. They are used to detect specific molecules, toxins, or gases in medical and environmental applications.
  
  
• Statement 4 is correct: Some studies suggest that modified carbon nanotubes can be broken down by enzymes and microorganisms through oxidation. However, their biodegradability varies depending on the modifications and conditions.
  
  

Thus, the correct answer is (c) 1, 3, and 4 only.

37. Consider the following activities:

[UPSC CSE Prelims 2020]

1. Spraying pesticides on a crop field
   
   
2. Inspecting the craters of active volcanoes
   
   
3. Collecting breath samples from spouting whales for DNA analysis
   
   

At the present level of technology, which of the above activities can be successfully carried out by using drones?

(a) 1 and 2 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (d)
 Explanation:

• Statement 1 is correct: Drones are widely used in agriculture for spraying pesticides. They help in precise application, reducing the amount of chemicals used and minimizing environmental impact. Drones are particularly useful in difficult-to-access terrains like terraced fields. Countries like Japan and China actively use drones for this purpose.
  
  
• Statement 2 is correct: Drones can be used to inspect craters of active volcanoes, allowing scientists to collect data on temperature, gas emissions, and geological changes. This method is much safer than sending humans into hazardous areas. Drones have been used for monitoring volcanoes such as Kīlauea in Hawaii.
  
  
• Statement 3 is correct: Drones are used to collect breath samples from spouting whales for DNA analysis. This technique is non-invasive and allows researchers to study whale genetics, health, and behavior without disturbing the animals. Research teams in Canada and the U.S. have successfully used drones for this purpose.
  
  

Thus, the correct answer is (d) 1, 2, and 3.

38. What is the importance of using Pneumococcal Conjugate Vaccines in India?

[UPSC CSE Prelims 2020]

1. These vaccines are effective against pneumonia as well as meningitis and sepsis.
   
   
2. Dependence on antibiotics that are not effective against drug-resistant bacteria can be reduced.
   
   
3. These vaccines have no side effects and cause no allergic reactions.
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 1 and 2 only
 (c) 3 only
 (d) 1, 2, and 3

Solution: (b)
 Explanation:

• Statement 1 is correct: Pneumococcal Conjugate Vaccines (PCVs) protect against infections caused by Streptococcus pneumoniae, including pneumonia, meningitis, and sepsis. These diseases primarily affect children and elderly individuals.
  
  
• Statement 2 is correct: PCVs help in reducing antibiotic use by preventing bacterial infections. This in turn helps in combating antibiotic resistance, which is a major global health concern.
  
  
• Statement 3 is incorrect: While PCVs are generally safe, they can have mild side effects, such as fever, redness, swelling at the injection site, and irritability. In rare cases, severe allergic reactions may occur.
  
  

Thus, the correct answer is (b) 1 and 2 only.

39. In the context of recent advances in human reproductive technology, "Pronuclear Transfer" is used for:

[UPSC CSE Prelims 2020]

(a) Fertilization of an egg in vitro by the donor sperm
 (b) Genetic modification of sperm-producing cells
 (c) Development of stem cells into functional embryos
 (d) Prevention of mitochondrial diseases in offspring

Solution: (d)
 Explanation:

• Pronuclear Transfer (PNT) is a reproductive technology used to prevent the transmission of mitochondrial diseases from mother to child.
  
  
• Mitochondrial diseases are genetic disorders caused by mutations in mitochondrial DNA (mtDNA), which is inherited solely from the mother.
  
  
• In PNT, the nuclear material from a fertilized egg with defective mitochondria is transferred into an enucleated donor egg with healthy mitochondria. This results in an embryo that has the nuclear DNA of the biological parents but the mitochondrial DNA of the donor woman.
  
  

Thus, the correct answer is (d) Prevention of mitochondrial diseases in offspring.

40. Consider the following statements (UPSC CSE Pre 2020)

1. Genetic changes can be introduced in the cells that produce eggs or sperms of a prospective parent.
   
   
2. A person's genome can be edited before birth at the early embryonic stage.
   
   
3. Human-induced pluripotent stem cells can be injected into the embryo of a pig.
   
   

Which of the statements given above is or are correct

1. 1 only
   b. 2 and 3 only
   c. 2 only
    d. 1, 2, and 3

Answer d

Explanation

Statement 1 is correct. Genetic modifications can be introduced in the germline cells sperm or egg cells using advanced techniques such as germline gene editing. This process has the potential to eliminate inherited genetic disorders.

Statement 2 is correct. CRISPR-Cas9 and similar gene-editing technologies allow for genome editing at the embryonic stage. This means genetic disorders can potentially be corrected before birth. However, such modifications are controversial due to ethical concerns.

Statement 3 is correct. Human-induced pluripotent stem cells hiPSCs can be injected into an animal embryo, such as that of a pig, to create chimeric animals. This technique is useful for research on human diseases and regenerative medicine.

41. With reference to solar water pumps, consider the following statements (UPSC CSE Pre 2020)

1. Solar power can be used for running surface pumps and not for submersible pumps.
   
   
2. Solar power can be used for running centrifugal pumps and not the ones with a piston.
   
   

Which of the statements given above is or are correct

1. 1 only
   b. 2 only
   c. Both 1 and 2
    d. Neither 1 nor 2

Answer d

Explanation

Statement 1 is incorrect. Solar-powered pumps can be used for both surface and submersible pumps. Submersible pumps, which operate underwater such as in borewells, can also function efficiently with solar energy.

Statement 2 is incorrect. Solar power can run both centrifugal pumps and positive displacement pumps piston pumps. Different types of solar pumps exist based on the requirement, including centrifugal, diaphragm, and helical rotor pumps.

Additional Information
 The PM-KUSUM scheme promotes the use of solar pumps among farmers in India.

42. With reference to communication technologies, what is or are the difference s between LTE Long-Term Evolution and VoLTE Voice over Long-Term Evolution UPSC CSE Pre 2019

1. LTE is commonly marketed as 3G, and VoLTE is commonly marketed as advanced 3G.
   
   
2. LTE is a data-only technology, and VoLTE is a voice-only technology.
   
   

Select the correct answer using the code given below

1. 1 only
   b. 2 only
   c. Both 1 and 2
    d. Neither 1 nor 2

Answer d

Explanation

Statement 1 is incorrect. LTE Long-Term Evolution is marketed as 4G technology, not 3G. VoLTE is an enhancement of LTE that allows high-definition voice calls over LTE networks.

Statement 2 is incorrect. LTE is not a data-only technology, it supports both voice and data. VoLTE is an upgrade that enables high-quality voice calls alongside LTE data services.

Key Differences between LTE and VoLTE

LTE is a data-only technology, while VoLTE supports both voice and data.
 LTE may not provide good quality voice calls while using data services, while VoLTE offers superior call quality, shorter call setup time, and simultaneous voice and data usage.
 LTE may turn off the data connection while making voice calls, while VoLTE does not turn off the data connection while making voice calls.
 LTE may require external applications to make video calls, while VoLTE does not require any external applications to make video calls.

43. In the context of digital technologies for entertainment, consider the following statements UPSC CSE Pre 2019

1. In Augmented Reality AR, a simulated environment is created, and the physical world is completely shut out.
   
   
2. In Virtual Reality VR, images generated from a computer are projected onto real-life objects or surroundings.
   
   
3. AR allows individuals to be present in the world and improves the experience using the camera of a smartphone or PC.
   
   
4. VR closes the world and transposes an individual, providing a complete immersion experience.
   
   

Which of the statements given above is or are correct

1. 1 and 2 only
   b. 3 and 4 only
   c. 1, 2, and 3 only
    d. 4 only

Answer b

Explanation

Statement 1 is incorrect. Augmented Reality AR does not completely shut out the physical world. Instead, it enhances the real world by overlaying virtual elements, such as in applications like Pokémon GO or AR navigation apps.

Statement 2 is incorrect. Virtual Reality VR does not project images onto real-life objects. Instead, it fully immerses the user in a virtual environment through headsets like Oculus Rift or HTC Vive.

Statement 3 is correct. AR enhances the real world using digital elements, accessible through smartphone cameras or AR glasses.

Statement 4 is correct. VR creates a fully immersive experience that shuts out the real world, making the user feel as though they are inside a completely different environment.

Key Differences between AR and VR

Augmented Reality AR allows users to interact with the real world with enhancements like digital overlays.
 Virtual Reality VR fully immerses users in a simulated digital environment.
 AR is used in applications like AR filters in mobile cameras, while VR is used in gaming, training simulations, and immersive experiences.

 

 

44. Consider the following statements (UPSC CSE Pre 2019)

1. A digital signature is an electronic record that identifies the certifying authority issuing it.
   
   
2. A digital signature is used as proof of identity for an individual to access information or a server on the internet.
   
   
3. A digital signature is an electronic method of signing an electronic document and ensuring that the original content remains unchanged.
   
   

Which of the statements given above is or are correct?

1. 1 only
   b. 2 and 3 only
   c. 3 only
    d. 1, 2, and 3

Answer: c

Explanation

Statement 1 is incorrect. A digital signature is not an electronic record identifying the certifying authority. Instead, that function is performed by a digital certificate, which contains the public key of an entity and is issued by a trusted authority.

Statement 2 is incorrect. Digital signatures are not primarily used for authentication or access control. Instead, they are used to ensure data integrity and non-repudiation. Authentication is a broader process that may involve digital signatures but is not limited to them.

Statement 3 is correct. A digital signature is a cryptographic mechanism used to sign electronic documents, ensuring that their contents remain unaltered.

How Digital Signatures Work

• A mathematical function (hash function) is applied to a document, generating a unique hash value.
  
  
• This hash value is encrypted with the sender’s private key, creating the digital signature.
  
  
• The recipient decrypts the signature using the sender’s public key and compares it with the hash of the received document.
  
  
• If both match, the document is verified as unchanged and authentic.
  
  

45. In the context of wearable technology, which of the following tasks can be performed by wearable devices? (UPSC CSE Pre 2019)

1. Identifying the location of a person
   
   
2. Monitoring a person’s sleep patterns
   
   
3. Assisting a hearing-impaired person
   
   

Select the correct answer using the code given below:

1. 1 only
   b. 2 and 3 only
   c. 3 only
    d. 1, 2, and 3

Answer: d

Explanation

Wearable technology includes devices designed to perform various functions, including health monitoring, fitness tracking, and accessibility enhancements.

Statement 1 is correct. Wearable devices, such as smartwatches and fitness bands, can track a person’s location using GPS and other positioning technologies. This is useful for navigation, fitness tracking, and safety applications.

Statement 2 is correct. Wearables, such as sleep trackers and smartwatches, monitor sleep patterns by analyzing movement, heart rate, and oxygen levels. These insights help users improve sleep quality.

Statement 3 is correct. Wearable devices can assist individuals with hearing impairments through sound amplification, noise reduction, and real-time captioning features. Smart hearing aids and bone-conduction headphones are examples of such devices.

46. Recently, scientists observed the merger of giant black holes billions of light-years away from Earth. What is the significance of this observation? (UPSC CSE Pre 2019)

1. The detection of Higgs boson particles.
   b. The detection of gravitational waves.
   c. Confirmation of intergalactic space travel through a wormhole.
    d. A deeper understanding of singularity.

Answer: b

Explanation

The observation of merging black holes provided crucial evidence for gravitational waves, which are ripples in spacetime caused by extreme cosmic events.

• Gravitational waves were first predicted by Albert Einstein’s theory of general relativity.
  
  
• The detection was made possible by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors.
  
  
• This discovery opened a new field of astronomy, allowing scientists to study cosmic events that are otherwise invisible through electromagnetic observations.
  
  

Why the other options are incorrect:

• Higgs boson detection (Option a): The Higgs boson was discovered at the Large Hadron Collider (LHC) in 2012, unrelated to black hole mergers.
  
  
• Intergalactic travel via wormholes (Option c): Wormholes remain a theoretical concept, and no evidence for their existence has been confirmed.
  
  
• Understanding singularity (Option d): While black hole mergers help us study black holes, they do not directly reveal the nature of singularities inside them.
  
  

This discovery of gravitational waves was a landmark achievement in astrophysics, earning the 2017 Nobel Prize in Physics.

47. For the measurement or estimation of which of the following are satellite images or remote sensing data used? (UPSC CSE Pre 2019)

1. Chlorophyll content in the vegetation of a specific location
   
   
2. Greenhouse gas emissions from rice paddies of a specific location
   
   
3. Land surface temperatures of a specific location
   
   

Select the correct answer using the code given below:

1. 1 only
   b. 2 and 3 only
   c. 3 only
    d. 1, 2, and 3

Answer: d

Explanation

Satellite-based remote sensing is widely used for environmental monitoring and resource management.

• Chlorophyll Content Estimation: Satellites use Normalized Difference Vegetation Index (NDVI) to assess vegetation health by analyzing how plants reflect different wavelengths of light. This helps in agricultural monitoring and ecosystem assessment.
  
  
• Greenhouse Gas (GHG) Emissions Monitoring: Remote sensing measures atmospheric concentrations of gases like carbon dioxide (CO₂) and methane (CH₄), including those from rice paddies, by analyzing reflected sunlight in specific wavelengths.
  
  
• Land Surface Temperature Mapping: Satellites detect thermal infrared radiation emitted by the Earth's surface to create temperature maps, aiding in climate studies, weather forecasting, and disaster management.
  
  

48. In the context of which one of the following are the terms 'pyrolysis and plasma gasification' mentioned? (UPSC CSE Pre 2019)

1. Extraction of rare earth elements
   b. Natural gas extraction technologies
   c. Hydrogen fuel-based automobiles
    d. Waste-to-energy technologies

Answer: d

Explanation

Pyrolysis and plasma gasification are advanced waste-to-energy technologies.

• Pyrolysis: A process in which organic materials are decomposed at high temperatures (above 430°C) in an oxygen-free environment, converting waste into biochar, syngas, and bio-oil.
  
  
• Plasma Gasification: A more advanced process using plasma torches to break down waste into its basic components, producing syngas (hydrogen + carbon monoxide), which can be used for energy generation.
  
  

These technologies help manage municipal solid waste, hazardous waste, and sewage sludge by converting them into useful energy.

49. Which one of the following statements is NOT correct? (UPSC CSE Pre 2019)

1. Hepatitis B virus is transmitted much like HIV.
   b. Hepatitis B, unlike Hepatitis C, does not have a vaccine.
   c. Globally, the numbers of people infected with Hepatitis B and C viruses are several times more than those infected with HIV.
    d. Some of those infected with Hepatitis B and C viruses do not show symptoms for many years.

Answer: b

Explanation

Statement b is incorrect because there is a vaccine for Hepatitis B, whereas Hepatitis C does not have a vaccine. The Hepatitis B vaccine is widely available and provides lifelong immunity in most cases.

Other statements are correct:

• Hepatitis B transmission is similar to HIV (through blood, semen, and other body fluids).
  
  
• More people are infected with Hepatitis B and C than HIV globally.
  
  
• Hepatitis B and C can remain asymptomatic for years, making them silent but serious infections.
  
  

50. Which of the following are reasons for the occurrence of multi-drug resistance in microbial pathogens in India? (UPSC CSE Pre 2019)

1. Genetic predisposition of some people
   
   
2. Taking incorrect doses of antibiotics to cure diseases
   
   
3. Using antibiotics in livestock farming
   
   
4. Multiple chronic diseases in some people
   
   

Select the correct answer using the code given below:

1. 1 and 2 only
   b. 2 and 3 only
   c. 1, 3, and 4 only
    d. 2, 3, and 4 only

Answer: b

Explanation

Multi-drug resistance (MDR) in microbial pathogens occurs due to human activities and misuse of antibiotics, not genetic predisposition.

• Incorrect antibiotic use (Statement 2): Taking incomplete or incorrect doses allows bacteria to develop resistance.
  
  
• Antibiotic use in livestock (Statement 3): Overuse in animals leads to resistant strains that can transfer to humans through food or the environment.
  
  

Genetic predisposition (Statement 1) and chronic diseases (Statement 4) do not cause MDR directly. Chronic diseases may make infections more severe, but they do not contribute to resistance development.

51. With reference to recent developments in science, which one of the following statements is NOT correct? (UPSC CSE Pre 2019)

1. Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
   b. Pieces of artificial functional DNA can be created in laboratories.
   c. A piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory.
    d. Cells taken out from plants and animals can be made to undergo cell division in laboratory petri dishes.

Answer: a

Explanation

Statement a is incorrect because while scientists can combine DNA from different species, it does not automatically form functional chromosomes. Chromosomes require complex structural proteins and regulatory elements beyond just DNA segments.

Other statements are correct:

• Artificial DNA synthesis (Statement b): Scientists can synthesize functional DNA sequences in labs, used in genetic engineering.
  
  
• DNA replication outside cells (Statement c): Polymerase Chain Reaction (PCR) allows DNA to be copied outside living cells.
  
  
• Cell division in lab conditions (Statement d): Tissue culture techniques enable plant and animal cells to divide and grow in petri dishes for research and cloning.

52. What is Cas9 protein that is often mentioned in the news? (UPSC CSE Pre 2019)

1. a) A molecular scissors used in targeted gene editing
   b) A biosensor used in the accurate detection of pathogens in patients
   c) A gene that makes plants pest-resistant
    d) A herbicidal substance synthesized in genetically modified crops

Answer: a

Explanation

Cas9 protein is a nuclease enzyme that acts as molecular scissors in the CRISPR-Cas9 gene-editing system.

• Derived from the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) system, which is a bacterial immune system protecting against viruses.
  
  
• It can be programmed to cut DNA at specific sequences, enabling precise gene modifications.
  
  
• Widely used in genetic research, including disease treatments, agriculture, and biotechnology.
  
  

53. 'RNA interference (RNAi)' technology has gained popularity in the last few years. Why? (UPSC CSE Pre 2019)

1. It is used in developing gene silencing therapies.
   
   
2. It can be used in developing therapies for the treatment of cancer.
   
   
3. It can be used to develop hormone replacement therapies.
   
   
4. It can be used to produce crop plants that are resistant to viral pathogens.
   
   

Select the correct answer using the code given below:

1. a) 1, 2, and 4
   b) 2 and 3 only
   c) 1 and 3 only
    d) 1 and 4 only

Answer: a

Explanation

• Statement 1 is correct: RNA interference (RNAi) is used for gene silencing, which helps treat diseases by blocking the expression of specific genes.
  
  
• Statement 2 is correct: RNAi can target cancer-related genes, preventing tumor growth.
  
  
• Statement 3 is incorrect: RNAi is not commonly used for hormone replacement therapies due to challenges like off-target effects and instability of RNA molecules.
  
  
• Statement 4 is correct: RNAi is used in agriculture to create virus-resistant crops by silencing viral genes that attack plants.
  
  

Thus, the correct answer is (a) 1, 2, and 4.

54. Consider the following statements: (UPSC CSE Pre 2019)

1. According to the Indian Patents Act, a biological process to create seed can be patented in India.
   
   
2. In India, there is no Intellectual Property Appellate Board.
   
   
3. Plant varieties are not eligible to be patented in India.
   
   

Which of the statements given above is/are correct?

1. a) 1 and 3 only
   b) 2 and 3 only
   c) 3 only
    d) 1, 2, and 3

Answer: c

Explanation

• Statement 1 is incorrect: Section 3(j) of the Indian Patents Act, 1970 states that plants, animals, seeds, and biological processes for their production are not patentable.
  
  
• Statement 2 is incorrect: The Intellectual Property Appellate Board (IPAB) was established in 2003 to handle patent disputes. However, it was abolished in 2021 and its functions were transferred to the High Courts.
  
  
• Statement 3 is correct: Plant varieties cannot be patented in India but are protected under the Protection of Plant Varieties and Farmers’ Rights Act, 2001.
  
  

Thus, the correct answer is (c) 3 only.

55. The word 'Denisovan' is sometimes mentioned in media in reference to: (UPSC CSE Pre 2019)

1. a) Fossils of a kind of dinosaurs
   b) An early human species
   c) A cave system found in North-East India
    d) A geological period in the history of the Indian subcontinent

Answer: b

Explanation

• Denisovans were an extinct species of archaic humans closely related to Neanderthals.
  
  
• They were first discovered in 2010 from a fossilized finger bone in Denisova Cave, Siberia.
  
  
• Their genetic traces are found in modern human populations, especially in Tibetans, Melanesians, and Aboriginal Australians.
  
  

Thus, the correct answer is (b) An early human species.

56. Consider the following techniques/phenomena: (UPSC CSE Pre 2019)

1. Budding and grafting in fruit plants
   
   
2. Cytoplasmic male sterility
   
   
3. Gene silencing
   
   

Which of the above is/are used to create transgenic crops?

1. a) 1 only
   b) 2 and 3 only
   c) 1 and 3 only
    d) None

Answer: (b) 2 and 3 only

Explanation

• Transgenic crops are genetically modified organisms (GMOs) that have genes artificially inserted from a different species or an unrelated plant.
  
  
• Budding and grafting (Statement 1) are not genetic modification techniques but methods of vegetative propagation used in horticulture.
  
  
• Cytoplasmic male sterility (Statement 2) is used in hybrid seed production and is often linked to genetic engineering.
  
  
• Gene silencing (Statement 3) is a genetic modification technique used to suppress undesirable traits in crops, making them resistant to viruses or improving their quality.
  
  

Thus, statements 2 and 3 are correct, and the correct answer is (b) 2 and 3 only.

57. The terms 'WannaCry, Petya and EternalBlue' sometimes mentioned in the news recently are related to: (UPSC CSE Pre 2018)

1. a) Exoplanets
   b) Cryptocurrency
   c) Cyberattacks
    d) Mini satellites

Answer: (c) Cyberattacks

Explanation

• WannaCry is a ransomware virus that locks a user’s device and demands ransom to unlock encrypted data.
  
  
• Petya is another ransomware that encrypts a system’s hard drive and demands a payment for restoration.
  
  
• EternalBlue is an exploit code that takes advantage of a Windows Server Message Block (SMB) vulnerability, allowing attackers to execute malicious code on compromised systems.
  
  
• These attacks primarily target Microsoft Windows operating systems and have affected various industries worldwide.
  
  

Thus, the correct answer is (c) Cyberattacks.

58. With reference to digital payments, consider the following statements: (UPSC CSE Pre 2018)

1. BHIM app allows the user to transfer money to anyone with a UPI-enabled bank account.
   
   
2. While a chip-PIN debit card has four factors of authentication, BHIM app has only two factors of authentication.
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: (a) 1 only

Explanation

• Statement 1 is correct: The BHIM app (Bharat Interface for Money) enables users to transfer money to anyone with a UPI-enabled bank account, or even to a regular bank account using IFSC code.
  
  
• Statement 2 is incorrect:
  
  
  • BHIM app has three levels of authentication, not two:
    
    
    1. The app binds with the device’s ID and mobile number.
       
       
    2. The user must sync their bank account (UPI or non-UPI enabled).
       
       
    3. The user must set up a PIN to access the app, along with the UPI PIN required for transactions.
       
       
  • On the other hand, a chip-PIN debit card has only two factors of authentication:
    
    
    1. The physical card
       
       
    2. The PIN entered during the transaction.
       
       

Thus, the correct answer is (a) 1 only.

59. Which of the following is/are the aim(s) of the 'Digital India' Plan of the Government of India? (UPSC CSE Pre 2018)

1. Formation of India's own Internet companies like China did.
   
   
2. Establish a policy framework to encourage overseas multinational corporations that collect Big Data to build their large data centres within our national geographical boundaries.
   
   
3. Connect many of our villages to the Internet and bring Wi-Fi to many of our schools, public places, and major tourist centres.
   
   

Select the correct answer using the code given below:

1. a) 1 and 2 only
   b) 3 only
   c) 2 and 3 only

Answer: (b) 3 only

Explanation

• Statement 1 is incorrect: The Digital India programme does not focus on creating Indian internet companies like China. Instead, it focuses on digital infrastructure, digital services, and digital empowerment.
  
  
• Statement 2 is incorrect: There is no explicit policy in the Digital India initiative that forces multinational corporations to establish data centers within India. However, data localization has been discussed separately in policies like the Personal Data Protection Bill.
  
  
• Statement 3 is correct: A major objective of the Digital India programme is to connect rural areas with high-speed Internet networks and improve digital access in public places, including schools and tourist centers.
  
  

Thus, the correct answer is (b) 3 only.

60. Consider the following statements: (UPSC CSE Pre 2018)

1. Aadhaar Card can be used as a proof of citizenship or domicile.
   
   
2. Once issued, Aadhaar number cannot be deactivated or omitted by the Issuing Authority.
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: (d) Neither 1 nor 2

Explanation

• Statement 1 is incorrect: According to the Unique Identification Authority of India (UIDAI), Aadhaar is not a proof of citizenship or domicile. It is only a proof of identity and residence. Even non-citizens residing in India can obtain an Aadhaar card if they meet the eligibility criteria.
  
  
• Statement 2 is incorrect: Aadhaar numbers can be deactivated or omitted under certain conditions, such as:
  
  
  • If the Aadhaar is found to be fraudulent or duplicate.
    
    
  • If issued to a foreign national or a non-resident.
    
    
  • If biometric data is found anomalous or inconsistent.
    
    
  • If the Aadhaar has not been used for three consecutive years.
    
    
• Since both statements are incorrect, the correct answer is (d) Neither 1 nor 2.
  
  

61. The identity platform 'Aadhaar' provides open 'Application Programming Interfaces (APIs)'. What does it imply? (UPSC CSE Pre 2018)

1. It can be integrated into any electronic device.
   
   
2. Online authentication using iris is possible.
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation

• Statement 1 is correct: Aadhaar provides open APIs, which means it allows third-party applications to access its data and services through a standardized interface. This makes it possible to integrate Aadhaar authentication into any electronic device that supports internet-based communication, such as mobile phones, biometric scanners, and laptops.
  
  
• Statement 2 is correct: Aadhaar authentication supports biometric verification, including iris scans. Devices equipped with an iris scanner can capture and encrypt the iris image of a user, sending it to the Aadhaar server for verification.
  
  
• Since both statements are correct, the correct answer is (c) Both 1 and 2.
  
  

62. Consider the following pairs: (UPSC CSE Pre 2018)

Experiment/Technology	Field
1. Belle II	Artificial Intelligence
2. Blockchain	Digital/Cryptocurrency Technology
3. CRISPR-Cas9	Particle Physics

Which of the pairs given above is/are correctly matched?

1. a) 1 and 3 only
   b) 2 only
   c) 2 and 3 only
    d) 1, 2 and 3

Answer: (b) 2 only

Explanation

• Pair 1 is incorrect: The Belle II experiment is a particle physics experiment that studies B mesons and other subatomic particles using a high-energy electron-positron collider. It is not related to Artificial Intelligence.
  
  
• Pair 2 is correct: Blockchain is a digital ledger technology that records transactions in a decentralized and tamper-proof manner. It is commonly associated with cryptocurrencies like Bitcoin and Ethereum.
  
  
• Pair 3 is incorrect: CRISPR-Cas9 is a gene-editing tool used to modify DNA sequences. It has applications in biotechnology and genetic engineering, but it is not related to particle physics.
  
  
• Since only Pair 2 is correct, the correct answer is (b) 2 only.
  
  

63. '3D printing' has applications in which of the following? (UPSC CSE Pre 2018)

1. Preparation of confectionery items
   
   
2. Manufacture of bionic ears
   
   
3. Automotive industry
   
   
4. Reconstructive surgeries
   
   
5. Data processing technologies
   
   

Select the correct answer using the code given below:

1. a) 1, 3 and 4 only
   b) 2, 3 and 5 only
   c) 1 and 4 only
    d) 1, 2, 3, 4 and 5

Answer: (d) 1, 2, 3, 4 and 5

Explanation

• 3D printing is a revolutionary technology that creates physical objects from digital models by adding material layer by layer. It has diverse applications, including:
  
  
  • Preparation of confectionery items (Statement 1): 3D printing is used in the food industry to create intricate and customized designs for chocolates and confectionery.
    
    
  • Manufacture of bionic ears (Statement 2): 3D printing is used in medical biotechnology to develop custom prosthetics, including bionic ears and artificial limbs.
    
    
  • Automotive industry (Statement 3): Car manufacturers use 3D printing for rapid prototyping, spare parts production, and designing lightweight components.
    
    
  • Reconstructive surgeries (Statement 4): 3D-printed implants and models help surgeons in complex reconstructive procedures.
    
    
  • Data processing technologies (Statement 5): 3D printing is used in electronics manufacturing, including customized circuit boards and components for computing hardware.
    
    
• Since all five applications are valid, the correct answer is (d) 1, 2, 3, 4 and 5.

64. When the alarm of your smartphone rings in the morning, you wake up and tap it to stop the alarm, which causes your geyser to be switched on automatically. The smart mirror in your bathroom shows the day's weather and also indicates the level of water in your overhead tank. After you take some groceries from your refrigerator for making breakfast, it recognizes the shortage of stock in it and places an order for fresh groceries. When you step out of your house and lock the door, all lights, fans, geysers, and ACs switch off automatically. On your way to the office, your car warns you about traffic congestion ahead and suggests an alternative route, and if you are late for a meeting, it sends a message to your office accordingly.

In the context of emerging communication technologies, which one of the following terms best applies to the above scenario?

1. a) Border Gateway Protocol
   b) Internet of Things
   c) Internet Protocol
    d) Virtual Private Network

Answer: (b) Internet of Things (IoT)

Explanation:

• Internet of Things (IoT) refers to a system where physical objects (such as smart home devices, appliances, and cars) are connected to the internet and can communicate with each other to automate various tasks.
  
  
• The scenario described in the question illustrates various IoT applications, including smart home automation, predictive inventory management, real-time traffic updates, and remote monitoring.
  
  
• Incorrect Options:
  
  
  • Border Gateway Protocol (BGP): A networking protocol used for routing data between different networks on the internet.
    
    
  • Internet Protocol (IP): A fundamental protocol for sending and receiving data packets across the internet but does not involve smart automation.
    
    
  • Virtual Private Network (VPN): A technology that encrypts internet connections to provide security and privacy, unrelated to the described IoT scenario.
    
    

Thus, the correct answer is (b) Internet of Things.

65. Consider the following phenomena:

1. Light is affected by gravity.
   
   
2. The Universe is constantly expanding.
   
   
3. Matter warps its surrounding space-time.
   
   

Which of the above is/are the predictions of Albert Einstein's General Theory of Relativity, often discussed in the media?

1. a) 1 and 2 only
   b) 3 only
   c) 1 and 3 only
    d) 1, 2 and 3

Answer: (d) 1, 2, and 3

Explanation:

• Statement 1 is correct: General Relativity predicts that gravity affects light by bending its path. This phenomenon, known as gravitational lensing, has been observed in astronomical events where massive objects, like black holes, distort the light passing near them.
  
  
• Statement 2 is correct: The expansion of the universe was a consequence of Einstein’s equations of General Relativity. Although Einstein initially introduced the cosmological constant (Λ) to maintain a static universe, later observations (such as those by Edwin Hubble) confirmed that the universe is expanding.
  
  
• Statement 3 is correct: General Relativity states that matter and energy warp space-time. Heavier objects create a gravitational field by distorting the space-time around them, which is the fundamental basis of gravity in this theory.
  
  

Since all three statements are correct, the correct answer is (d) 1, 2, and 3.

66. With reference to the Indian Regional Navigation Satellite System (IRNSS), consider the following statements:

1. IRNSS has three satellites in geostationary orbit and four satellites in geosynchronous orbit.
   
   
2. IRNSS covers entire India and about 5500 sq. km beyond its borders.
   
   
3. India will have its own satellite navigation system with full global coverage by the middle of 2019.
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 1 and 2 only
   c) 2 and 3 only
    d) None of the above

Answer: (a) 1 only

Explanation:

• Statement 1 is correct: The Indian Regional Navigation Satellite System (IRNSS), also known as NavIC, consists of seven satellites:
  
  
  • Three satellites are placed in geostationary orbit (fixed above the equator).
    
    
  • Four satellites are placed in geosynchronous orbit (orbits inclined to the equator but synchronized with Earth's rotation).
    
    
• Statement 2 is incorrect: IRNSS primarily covers India and up to 1500 km beyond its borders, not 5500 sq. km. This coverage is intended for regional navigation purposes.
  
  
• Statement 3 is incorrect: IRNSS is not a global navigation system. It is a regional system, and as of 2019, India had not expanded NavIC into a full-fledged global navigation system like the Global Positioning System (GPS) of the USA or Galileo of the European Union.
  
  

Since only Statement 1 is correct, the correct answer is (a) 1 only.

67. In which of the following areas can GPS technology be used? (UPSC CSE Prelims 2018)

1. Mobile phone operations
   
   
2. Banking operations
   
   
3. Controlling the power grids
   
   

Select the correct answer using the codes given below:

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Answer: (d) 1, 2, and 3

Explanation:

Global Positioning System (GPS) is a satellite-based navigation system that provides location, time, and velocity data to users worldwide. It has applications in various sectors:

• Mobile phone operations (Correct):
  
  
  • GPS is used in smartphones for navigation, location tracking, emergency services, and mobile applications like Google Maps and ride-hailing services.
    
    
• Banking operations (Correct):
  
  
  • Banks use GPS for location verification of ATMs, fraud detection, secure financial transactions, and tracking mobile banking vehicles.
    
    
• Controlling power grids (Correct):
  
  
  • GPS technology helps synchronize the operations of power grids by providing precise timing signals, which are essential for load balancing, grid security, and real-time fault detection.
    
    

Since all three statements are correct, the answer is (d) 1, 2, and 3.

68. With reference to India's satellite launch vehicles, consider the following statements: (UPSC CSE Prelims 2018)

1. PSLVs launch satellites useful for Earth resources monitoring, whereas GSLVs are designed mainly to launch communication satellites.
   
   
2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
   
   
3. GSLV Mk III is a four-stage launch vehicle with the first and third stages using solid rocket motors, and the second and fourth stages using liquid rocket engines.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 2 only
 (d) 3 only

Answer: (a) 1 only

Explanation:

• Statement 1 is correct:
  
  
  • Polar Satellite Launch Vehicles (PSLV) are primarily used to launch satellites for Earth observation, remote sensing, and scientific missions.
    
    
  • Geosynchronous Satellite Launch Vehicles (GSLV) are designed to launch heavy payloads into geosynchronous orbits, mainly for telecommunications, broadcasting, and navigation.
    
    
• Statement 2 is incorrect:
  
  
  • Satellites launched by PSLV are placed in polar orbits or sun-synchronous orbits. These satellites move across the Earth in a fixed pattern but do not remain stationary relative to a specific point.
    
    
  • Only geostationary satellites, mostly launched by GSLV, remain fixed in the sky as seen from Earth.
    
    
• Statement 3 is incorrect:
  
  
  • GSLV Mk III is a three-stage launch vehicle, not four-stage.
    
    
  • The first stage consists of two solid rocket boosters, the core stage is liquid-fueled, and the third stage is cryogenic (using liquid hydrogen and oxygen).
    
    

Since only Statement 1 is correct, the answer is (a) 1 only.

69. What is 'Terminal High Altitude Area Defense (THAAD)', sometimes seen in the news? (UPSC CSE Prelims 2018)

(a) An Israeli radar system
 (b) India's indigenous anti-missile programme
 (c) An American anti-missile system
 (d) A defence collaboration between Japan and South Korea

Answer: (c) An American anti-missile system

Explanation:

• Terminal High Altitude Area Defense (THAAD) is an American missile defense system designed to intercept and destroy short-, medium-, and intermediate-range ballistic missiles during their terminal phase (final descent).
  
  
• THAAD was developed after the Gulf War (1991) in response to Iraq's Scud missile attacks.
  
  
• The system uses hit-to-kill technology, meaning it destroys the target missile by direct impact rather than carrying an explosive warhead.
  
  
• THAAD has been deployed in South Korea, Japan, Guam, and the United States to counter missile threats from adversaries like North Korea and Iran.
  
  

Thus, the correct answer is (c) An American anti-missile system.

70. With reference to the Genetically Modified (GM) mustard developed in India, consider the following statements: (UPSC CSE Prelims 2018)

1. GM mustard has the genes of a soil bacterium that give the plant the property of pest resistance to a wide variety of pests.
   
   
2. GM mustard has the genes that allow the plant cross-pollination and hybridization.
   
   
3. GM mustard has been developed jointly by the IARI and Punjab Agricultural University.
   
   

Which of the statements given above is/are correct?

(a) 1 and 3 only
 (b) 2 only
 (c) 2 and 3 only
 (d) 1, 2, and 3

Answer: (b) 2 only

Explanation:

• Statement 1 is incorrect:
  
  
  • GM mustard does not have genes from a soil bacterium for pest resistance.
    
    
  • Instead, it has been genetically modified using barnase-barstar technology to facilitate hybrid seed production, improving yield and productivity.
    
    
  • Unlike Bt cotton, which has pest-resistant genes from Bacillus thuringiensis, GM mustard does not provide resistance to pests like aphids or whiteflies.
    
    
• Statement 2 is correct:
  
  
  • GM mustard is designed for hybridization. Mustard is typically a self-pollinating plant, but the barnase-barstar gene system allows cross-pollination, leading to higher-yield hybrids.
    
    
• Statement 3 is incorrect:
  
  
  • GM mustard (variety DMH-11) was developed by the Centre for Genetic Manipulation of Crop Plants (CGMCP) at Delhi University, not IARI or Punjab Agricultural University.
    
    
  • The research was supported by the National Dairy Development Board (NDDB) and the Indian Council of Agricultural Research (ICAR).
    
    

Since only Statement 2 is correct, the answer is (b) 2 only.

71. Consider the following statements: (UPSC CSE Prelims 2018)

1. The Earth's magnetic field has reversed every few hundred thousand years.
   
   
2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
   
   
3. When living organisms originated, they modified the early atmosphere of the Earth.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Answer: (c) 1 and 3 only

Explanation:

• Statement 1 is correct:
  
  
  • Earth's geomagnetic field reverses periodically, a phenomenon known as geomagnetic reversal.
    
    
  • This occurs every few hundred thousand years on average, with the last reversal happening around 780,000 years ago (Brunhes-Matuyama reversal).
    
    
• Statement 2 is incorrect:
  
  
  • When Earth was formed around 4.5 billion years ago, its early atmosphere mainly contained hydrogen, methane, ammonia, and carbon dioxide, but little to no oxygen.
    
    
  • The claim that oxygen was 54% is incorrect. The atmosphere only became oxygen-rich after the Great Oxygenation Event (~2.4 billion years ago), driven by cyanobacteria.
    
    
• Statement 3 is correct:
  
  
  • Early photosynthetic organisms (cyanobacteria) released oxygen into the atmosphere, significantly altering its composition and leading to the formation of an oxygen-rich environment.
    
    

Thus, the correct answer is (c) 1 and 3 only.

72. With reference to solar power production in India, consider the following statements: (UPSC CSE Prelims 2018)

1. India is the third largest in the world in the manufacture of silicon wafers used in photovoltaic units.
   
   
2. The solar power tariffs are determined by the Solar Energy Corporation of India (SECI).
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Answer: (d) Neither 1 nor 2

Explanation:

• Statement 1 is incorrect:
  
  
  • India does not produce silicon wafers used in photovoltaic units at a large scale. Most solar panels in India are assembled using imported components, mainly from China, Taiwan, and Malaysia.
    
    
  • As of 2018, India was not among the top three producers of silicon wafers.
    
    
• Statement 2 is incorrect:
  
  
  • The Solar Energy Corporation of India (SECI) is a government agency that promotes solar energy projects but does not set solar power tariffs.
    
    
  • Solar power tariffs are determined by the State Electricity Regulatory Commissions (SERCs) based on competitive bidding and market dynamics.
    
    

Since both statements are incorrect, the answer is (d) Neither 1 nor 2.

73. In India, it is legally mandatory for which of the following to report on cybersecurity incidents? (UPSC CSE Prelims 2017)

1. Service providers
   
   
2. Data centers
   
   
3. Body corporate
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 1 and 2 only
 (c) 3 only
 (d) 1, 2, and 3

Answer: (d) 1, 2, and 3

Explanation:

• As per the directive issued by CERT-In (Indian Computer Emergency Response Team) on April 28, 2022, it is mandatory for the following entities to report cybersecurity incidents within six hours of detection:
  
  
  • Service providers (e.g., internet service providers, telecom companies).
    
    
  • Data centers (e.g., cloud computing services, hosting companies).
    
    
  • Body corporates (e.g., businesses and private firms).
    
    
• This mandate ensures rapid response and mitigation of cyber threats affecting national infrastructure and private enterprises.
  
  

Since all three categories must report cybersecurity incidents, the correct answer is (d) 1, 2, and 3.

74. The terms 'Event Horizon', 'Singularity', 'String Theory' and 'Standard Model' are sometimes seen in the news in the context of: (UPSC CSE Prelims 2017)

(a) Observation and understanding of the Universe
 (b) Study of the solar and lunar eclipses
 (c) Placing satellites in the orbit of the Earth
 (d) Origin and evolution of living organisms on the Earth

Answer: (a) Observation and understanding of the Universe

Explanation:

• Event Horizon: The boundary around a black hole beyond which nothing, not even light, can escape.
  
  
• Singularity: A point in space where gravity becomes infinitely strong, typically at the center of a black hole.
  
  
• String Theory: A theoretical framework that attempts to unify quantum mechanics and general relativity, suggesting that fundamental particles are tiny vibrating strings.
  
  
• Standard Model: A fundamental framework in physics that describes elementary particles and their interactions (excluding gravity).
  
  

Since all these concepts relate to the study of the universe and cosmology, the correct answer is (a) Observation and understanding of the Universe.

75. Consider the following in respect of Indian Ocean Naval Symposium (IONS): (UPSC CSE Prelims 2017)

1. The inaugural IONS was held in India in 2015 under the chairmanship of the Indian Navy.
   
   
2. IONS is a voluntary initiative that seeks to increase maritime cooperation among navies of the littoral states of the Indian Ocean Region.
   
   

Which of the above statements is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Answer: (b) 2 only

Explanation:

• Statement 1 is incorrect: The inaugural IONS was held in Abu Dhabi, UAE, in 2008 under the chairmanship of the United Arab Emirates Navy, not in India in 2015.
  
  
• Statement 2 is correct: IONS is a voluntary maritime cooperation initiative among Indian Ocean littoral states to enhance maritime security, collaboration, and confidence-building. It has 24 member states and fosters cooperation through exercises, information exchange, and joint activities.
  
  

Thus, the correct answer is (b) 2 only.

76. Organic Light Emitting Diodes (OLEDs) are used to create digital displays in many devices. What is the advantage of OLED displays over Liquid Crystal Displays (LCDs)? (UPSC CSE Prelims 2017)

1. OLED displays can be fabricated on flexible plastic substrates.
   
   
2. Roll-up displays embedded in clothing can be made using OLEDs.
   
   
3. Transparent displays are possible using OLEDs.
   
   

Select the correct answer using the code given below:

(a) 1 and 3 only
 (b) 2 only
 (c) 1, 2, and 3
 (d) None of the above statements is correct

Answer: (c) 1, 2, and 3

Explanation:

• Statement 1 is correct: OLEDs can be fabricated on flexible plastic substrates, allowing for the creation of bendable, foldable, and rollable
  
  
• Statement 2 is correct: Roll-up OLED displays embedded in clothing are possible due to the material’s flexibility and thinness. Some companies have already developed wearable OLED displays.
  
  
• Statement 3 is correct: OLEDs allow for transparent displays, making applications such as smart windows and augmented reality glasses
  
  

Since all statements are correct, the answer is (c) 1, 2, and 3.

77. Consider the following statements: (UPSC CSE Prelims 2017)

1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue.
   
   
2. Sexual transmission of Zika virus disease is possible.
   
   

Which of the statements given above is/are correct?

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation:

• Statement 1 is correct: Zika virus is primarily transmitted by Aedes mosquitoes, the same genus that spreads dengue and chikungunya.
  
  
• Statement 2 is correct: Zika virus can be transmitted sexually from an infected person to their partner. It has also been detected in blood transfusions.
  
  

Since both statements are correct, the answer is (c) Both 1 and 2.

78. What is the application of Somatic Cell Nuclear Transfer (SCNT) Technology? (UPSC CSE Prelims 2017)

(a) Production of bio-larvicides
 (b) Manufacture of biodegradable plastics
 (c) Reproductive cloning of animals
 (d) Production of organisms free of diseases

Answer: (c) Reproductive cloning of animals

Explanation:

• Somatic Cell Nuclear Transfer (SCNT) is a cloning technique where the nucleus of a somatic cell (a non-reproductive cell) is transferred into an enucleated egg cell (an egg cell whose nucleus has been removed).
  
  
• The egg is then stimulated to develop into an embryo, which is implanted into a surrogate mother.
  
  
• This method was famously used to create Dolly the sheep, the first cloned mammal.
  
  
• SCNT has been applied to clone animals like cows, pigs, horses, and even endangered species.
  
  

Thus, the correct answer is (c) Reproductive cloning of animals.

79. With reference to agriculture in India, how can the technique of 'genome sequencing', often seen in the news, be used in the immediate future? (UPSC CSE Prelims 2017)

1. Genome sequencing can be used to identify genetic markers for disease resistance and drought tolerance in various crop plants.
   
   
2. This technique helps in reducing the time required to develop new varieties of crop plants.
   
   
3. It can be used to decipher the host-pathogen relationship in crops.
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Answer: (d) 1, 2, and 3

Explanation:

• Statement 1 is correct: Genome sequencing helps identify genetic markers for traits such as disease resistance and drought tolerance in crops. This enables the breeding of climate-resilient and disease-resistant crops.
  
  
• Statement 2 is correct: Traditional breeding methods take years, but genome sequencing accelerates the process by allowing scientists to quickly identify beneficial genes.
  
  
• Statement 3 is correct: Understanding the host-pathogen relationship through genome sequencing helps in developing disease-resistant crops and effective pest management strategies.
  
  

Since all three statements are correct, the answer is (d) 1, 2, and 3.

80. What is the purpose of the 'Evolved Laser Interferometer Space Antenna (eLISA) project'? (UPSC CSE Prelims 2017)

(a) To detect neutrinos
 (b) To detect gravitational waves
 (c) To detect the effectiveness of missile defense systems
 (d) To study the effect of solar flares on our communication systems

Answer: (b) To detect gravitational waves

Explanation:

• Evolved Laser Interferometer Space Antenna (eLISA) is a European Space Agency (ESA) project designed to detect and measure gravitational waves in space.
  
  
• It consists of a constellation of three spacecraft in an equilateral triangle formation, each separated by millions of kilometers.
  
  
• Gravitational waves were first predicted by Albert Einstein’s General Theory of Relativity, and eLISA aims to study these waves in space, beyond the limitations of Earth-based detectors like LIGO (Laser Interferometer Gravitational-Wave Observatory).
  
  

Thus, the correct answer is (b) To detect gravitational waves.

81. With reference to 'LiFi', recently in the news, which of the following statements is/are correct? (UPSC CSE Prelims 2016)

1. It uses light as the medium for high-speed data transmission.
   
   
2. It is a wireless technology and is several times faster than WiFi.
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation:

• Statement 1 is correct: LiFi (Light Fidelity) is a wireless communication technology that uses visible light (instead of radio waves) to transmit data. It works through LED bulbs that blink at ultra-high speeds, invisible to the human eye.
  
  
• Statement 2 is correct: LiFi is significantly faster than WiFi, with potential speeds reaching 100 Gbps, compared to WiFi’s several hundred Mbps to a few Gbps.
  
  

Thus, the correct answer is (c) Both 1 and 2.

82. With reference to 'Astrosat', the astronomical observatory launched by India, which of the following statements is/are correct? (UPSC CSE Prelims 2016)

1. Other than the USA and Russia, India is the only country to have launched a similar observatory into space.
   
   
2. Astrosat is a 2000 kg satellite placed in an orbit at 1650 km above the surface of the Earth.
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Answer: (d) Neither 1 nor 2

Explanation:

• Statement 1 is incorrect: India is not the only country besides the USA and Russia to have launched a space observatory. Other countries such as Japan (Suzaku, Hitomi), Europe (XMM-Newton, Planck), and Russia (Spektr-RG X-ray) have also launched space-based astronomical observatories.
  
  
• Statement 2 is incorrect: Astrosat has a lift-off mass of 1515 kg, not 2000 kg. Additionally, it was placed in a low Earth orbit of 650 km, not 1650 km.

83. Consider the following statements regarding Mangalyaan, launched by ISRO: (UPSC CSE Prelims 2016)

1. It is also called the Mars Orbiter Mission.
   
   
2. It made India the second country to have a spacecraft orbit Mars after the USA.
   
   
3. It made India the only country to be successful in making its spacecraft orbit Mars on its very first attempt.
   
   

Select the correct answer using the code given below:

(a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Answer: (c) 1 and 3 only

Explanation:

• Statement 1 is correct: The Mars Orbiter Mission (MOM), also known as Mangalyaan, was launched by ISRO on November 5, 2013, and successfully entered Mars' orbit on September 24, 2014.
  
  
• Statement 2 is incorrect: Mangalyaan made India the fourth country to successfully reach Mars, after the USA, the Soviet Union, and the European Space Agency (ESA).
  
  
• Statement 3 is correct: India became the first country to successfully place a spacecraft in Mars’ orbit on its maiden attempt. The UAE's Hope mission (2020) became the second such mission to achieve this feat.
  
  

Thus, the correct answer is (c) 1 and 3 only. 🚀

84. Which one of the following best describes 'INS Astradharini', recently in the news? (UPSC CSE Prelims 2016)

(a) Amphibious warfare ship
 (b) Nuclear-powered submarine
 (c) Torpedo launch and recovery vessel
 (d) Nuclear-powered aircraft carrier

Answer: (c) Torpedo launch and recovery vessel

Explanation:

• INS Astradharini is an indigenously designed and built torpedo launch and recovery vessel (TLRV) for the Indian Navy.
  
  
• It was commissioned on October 6, 2015, at Visakhapatnam Naval Base.
  
  
• It is 50 meters long, weighs 500 tons, and can travel at a maximum speed of 15 knots.
  
  
• The vessel is used to test torpedoes, underwater weapons, and sensors.
  
  

Thus, the correct answer is (c) Torpedo launch and recovery vessel. ⚓

85. A recent movie titled 'The Man Who Knew Infinity' is based on the biography of: (UPSC CSE Prelims 2016)

(a) S. Ramanujan
 (b) S. Chandrashekhar
 (c) S. N. Bose
 (d) C.V. Raman

Answer: (a) S. Ramanujan

Explanation:

• The Man Who Knew Infinity (2015) is a biographical film based on the life of the Indian mathematical genius Srinivasa Ramanujan.
  
  
• The movie is adapted from the book The Man Who Knew Infinity: A Life of the Genius Ramanujan by Robert Kanigel.
  
  
• It depicts Ramanujan’s journey from India to Cambridge University, where he worked with H. Hardy and made groundbreaking contributions to number theory, infinite series, and mathematical analysis.
  
  

Thus, the correct answer is (a) S. Ramanujan. 📚

86. Which of the following statements are correct? Viruses can infect: (UPSC CSE Prelims 2016)

1. Bacteria
   
   
2. Fungi
   
   
3. Plants
   
   

Select the correct answer using the code given below:

(a) 1 and 2 only
 (b) 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Answer: (d) 1, 2, and 3

Explanation:

• Viruses can infect all forms of life, including bacteria (bacteriophages), fungi, and plants.
  
  
• Bacteriophages are viruses that infect bacteria.
  
  
• Mycoviruses infect fungi.
  
  
• Several viruses, such as tobacco mosaic virus (TMV), infect plants.
  
  

Thus, the correct answer is (d) 1, 2, and 3.

87. In the context of developments in bioinformatics, the term 'transcriptome', sometimes seen in the news, refers to: (UPSC CSE Prelims 2016)

(a) A range of enzymes used in genome editing
 (b) The full range of mRNA molecules expressed by an organism
 (c) The description of the mechanism of gene expression
 (d) A mechanism of genetic mutations taking place in cells

Answer: (b) The full range of mRNA molecules expressed by an organism

Explanation:

• The transcriptome is the complete set of RNA transcripts produced by the genome under specific conditions or in a specific cell type.
  
  
• It includes messenger RNA (mRNA), which carries genetic information from DNA to ribosomes for protein synthesis.
  
  
• Transcriptomics is used in research areas like disease mechanisms, gene expression, and biomarker discovery.
  
  

Thus, the correct answer is (b) The full range of mRNA molecules expressed by an organism. 🧬

88. What is 'Greased Lightning-10 (GL-10)', recently in the news? (UPSC CSE Prelims 2016)

(a) Electric plane tested by NASA
 (b) Solar-powered two-seater aircraft designed by Japan
 (c) Space observatory launched by China
 (d) Reusable rocket designed by ISRO

Answer: (a) Electric plane tested by NASA

Explanation:

• Greased Lightning-10 (GL-10) is a battery-powered vertical takeoff and landing (VTOL) aircraft developed by NASA.
  
  
• It is a 10-engine, remotely piloted aircraft that can take off like a helicopter and then transition into airplane flight
  
  
• The project aims to test electric propulsion systems for future aircraft.
  
  

Thus, the correct answer is (a) Electric plane tested by NASA. ✈️

89. India is an important member of the 'International Thermonuclear Experimental Reactor' (ITER). If this experiment succeeds, what is the immediate advantage for India? (UPSC CSE Prelims 2016)

(a) It can use thorium in place of uranium for power generation
 (b) It can attain a global role in satellite navigation
 (c) It can drastically improve the efficiency of its fission reactors in power generation
 (d) It can build fusion reactors for power generation

Answer: (d) It can build fusion reactors for power generation

Explanation:

• ITER (International Thermonuclear Experimental Reactor) is a collaborative nuclear fusion project involving countries like India, the EU, USA, China, Japan, Russia, and South Korea.
  
  
• It aims to generate energy through nuclear fusion, the same process that powers the Sun.
  
  
• If successful, India will gain expertise in building fusion reactors, leading to a clean and nearly unlimited energy source.
  
  

Thus, the correct answer is (d) It can build fusion reactors for power generation. 🌞

90. In which of the following activities are Indian Remote Sensing (IRS) satellites used? (UPSC CSE Prelims 2015)

1. Assessment of crop productivity
   
   
2. Locating groundwater resources
   
   
3. Mineral exploration
   
   
4. Telecommunications
   
   
5. Traffic studies
   
   

Select the correct answer using the code given below:

(a) 1, 2, and 3 only
 (b) 4 and 5 only
 (c) 1 and 2 only
 (d) 1, 2, 3, 4, and 5

Answer: (a) 1, 2, and 3 only

Explanation:

Indian Remote Sensing (IRS) satellites are used for:
 ✅ Crop productivity assessment – Monitoring crop health, yield prediction, and agricultural planning.
 ✅ Locating groundwater resources – Identifying potential water sources using satellite imagery.
 ✅ Mineral exploration – Mapping geological formations to detect mineral deposits.

However, IRS satellites are not directly used for telecommunications or traffic studies.

Thus, the correct answer is (a) 1, 2, and 3 only.

91. With reference to 'Near Field Communication (NFC) Technology', which of the following statements is/are correct? (UPSC CSE Prelims 2015)

1. It is a contactless communication technology that uses electromagnetic radio fields.
   
   
2. NFC is designed for use by devices which can be at a distance of even a metre from each other.
   
   
3. NFC can use encryption when sending sensitive information.
   
   

Select the correct answer using the code given below:

1. a) 1 and 2 only
   b) 3 only
   c) 1 and 3 only
    d) 1, 2 and 3

Answer: c) 1 and 3 only

Explanation

Statement 1 is correct
 Near Field Communication NFC is a short-range wireless communication technology. It works using electromagnetic radio fields to enable contactless communication between devices. It is used in mobile payments such as Google Pay and Apple Pay, contactless cards, and access control systems.

Statement 2 is incorrect
 NFC works only within a very short range typically less than 4 cm or 1.5 inches. It cannot work at a distance of even one metre.

Statement 3 is correct
 NFC can use encryption when transferring sensitive information, such as in mobile payments and secure authentication.

Thus, the correct answer is c 1 and 3 only.

92. With reference to the use of nanotechnology in the health sector, which of the following statements is/are correct? (UPSC CSE Prelims 2015)

1. Targeted drug delivery is made possible by nanotechnology.
   
   
2. Nanotechnology can largely contribute to gene therapy.
   
   

Select the correct answer using the code given below:

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: c) Both 1 and 2

Explanation

• Statement 1 is correct: Nanotechnology enables targeted drug delivery by using nanoparticles to deliver drugs directly to diseased cells, reducing side effects and improving treatment efficiency.
  
  
• Statement 2 is correct: Nanotechnology plays a significant role in gene therapy by using nanocarriers to deliver genetic material safely and efficiently into cells.
  
  

Thus, the correct answer is c) Both 1 and 2.

93. Which of the following statements is/are correct regarding National Innovation Foundation-India (NIF)? (UPSC CSE Prelims 2015)

1. NIF is an autonomous body of the Department of Science and Technology under the Central Government.
   
   
2. NIF is an initiative to strengthen the highly advanced scientific research in India's premier scientific institutions in collaboration with highly advanced foreign scientific institutions.
   
   

Select the correct answer using the code given below:

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: a) 1 only

Explanation

• Statement 1 is correct: NIF is an autonomous body under the Department of Science and Technology, Government of India. It promotes grassroots innovations and supports local inventors.
  
  
• Statement 2 is incorrect: NIF focuses on grassroots innovation rather than advanced scientific research in collaboration with foreign institutions.
  
  

Thus, the correct answer is a) 1 only.

94. The term 'IndARC', sometimes seen in the news, is the name of: (UPSC CSE Prelims 2015)

1. a) An indigenously developed radar system inducted into Indian Defence.
   b) India's satellite to provide services to the countries of the Indian Ocean Rim.
   c) A scientific establishment set up by India in the Antarctic region.
    d) India's underwater observatory to scientifically study the Arctic region.

Answer: d) India's underwater observatory to scientifically study the Arctic region

Explanation

• IndARC is India's first underwater moored observatory in the Arctic Ocean.
  
  
• It was deployed in 2014 to study climate change and environmental parameters in the Arctic region.
  
  

Thus, the correct answer is d) India's underwater observatory to scientifically study the Arctic region.

95. H1N1 virus is sometimes mentioned in the news with reference to which one of the following diseases? (UPSC CSE Prelims 2015)

1. a) AIDS
   b) Bird Flu
   c) Dengue
    d) Swine Flu

Answer: d) Swine Flu

Explanation

• The H1N1 virus is responsible for Swine Flu, which caused a pandemic in 2009.
  
  
• It is a subtype of the influenza A virus that spreads among humans and pigs.
  
  

Thus, the correct answer is d) Swine Flu.

96. With reference to 'fuel cells' in which hydrogen-rich fuel and oxygen are used to generate electricity, consider the following statements: (UPSC CSE Prelims 2015)

1. If pure hydrogen is used as a fuel, the fuel cell emits heat and water as by-products.
   
   
2. Fuel cells can be used for powering buildings and not for small devices like laptop computers.
   
   
3. Fuel cells produce electricity in the form of Alternating Current (AC).
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 2 and 3 only
   c) 1 and 3 only
    d) 1, 2 and 3

Answer: a) 1 only

Explanation

• Statement 1 is correct: When pure hydrogen is used as fuel, the only by-products of fuel cells are heat and water. This makes them an environmentally friendly energy source.
  
  
• Statement 2 is incorrect: Fuel cells can be used for both large-scale applications like powering buildings and small-scale devices like laptops and smartphones.
  
  
• Statement 3 is incorrect: Fuel cells generate electricity in the form of Direct Current (DC), not Alternating Current (AC).
  
  

Thus, the correct answer is a) 1 only.

97. With reference to bio-toilets used by the Indian Railways, consider the following statements: (UPSC CSE Prelims 2015)

1. The decomposition of human waste in the bio-toilets is initiated by a fungal inoculum.
   
   
2. Ammonia and water vapor are the only end products in this decomposition which are released into the atmosphere.
   
   

Which of the statements given above is/are correct?

1. a) 1 only
   b) 2 only
   c) Both 1 and 2
    d) Neither 1 nor 2

Answer: d) Neither 1 nor 2

Explanation

• Statement 1 is incorrect: The decomposition in bio-toilets is initiated by bacterial inoculum, not fungal inoculum. The bacteria break down waste into simpler compounds.
  
  
• Statement 2 is incorrect: The end products of the decomposition process include methane, carbon dioxide, and water, not just ammonia and water vapor.
  
  

Thus, the correct answer is d) Neither 1 nor 2.

98. With reference to 'fly ash' produced by power plants using coal as fuel, which of the following statements is/are correct?

(UPSC CSE Pre 2015)

1. Fly ash can be used in the production of bricks for building construction.
   
   
2. Fly ash can be used as a replacement for some of the Portland cement in concrete.
   
   
3. Fly ash is made up of silicon dioxide and calcium oxide only and does not contain any toxic elements.
   
   

Answer: (a) 1 and 2 only

Explanation:

• Statement 1 is correct: Fly ash, a byproduct of coal combustion in power plants, is used to manufacture bricks and other construction materials. Fly ash bricks are lightweight, strong, and eco-friendly compared to traditional clay bricks.
  
  
• Statement 2 is correct: Fly ash is widely used as a partial replacement for Portland cement in concrete, improving its durability, workability, and resistance to sulfate attacks.
  
  
• Statement 3 is incorrect: Fly ash contains silicon dioxide (SiO₂) and calcium oxide (CaO), but it may also contain trace amounts of toxic elements like arsenic, mercury, and lead, which can be hazardous if not properly managed.
  
  

99. In the context of modern scientific research, consider the following statements about 'IceCube', a particle detector located at the South Pole:

(UPSC CSE Pre 2015)

1. It is the world's largest neutrino detector, encompassing a cubic kilometre of ice.
   
   
2. It is a powerful telescope to search for dark matter.
   
   
3. It is buried deep in the ice.
   
   

Answer: (d) 1, 2, and 3

Explanation:

• Statement 1 is correct: IceCube is the world's largest neutrino detector, covering a volume of about 1 cubic kilometre of Antarctic ice. It is designed to detect neutrinos, which are subatomic particles that rarely interact with matter.
  
  
• Statement 2 is correct: IceCube is used to search for dark matter and other cosmic phenomena by detecting high-energy neutrinos that may originate from black holes, supernovae, or other astrophysical sources.
  
  
• Statement 3 is correct: IceCube is located deep beneath the Antarctic ice, around 5 to 2.5 kilometres below the surface, where the ice acts as a natural filter to reduce background noise from cosmic rays.
  
  

100. Which of the following is/are correctly matched?

(UPSC CSE Pre 2014)

Spacecraft	Purpose
1. Cassini-Huygens	Orbiting Venus and transmitting data to Earth
2. Messenger	Mapping and investigating Mercury
3. Voyager 1 and 2	Exploring the outer solar system

Answer: (b) 2 and 3 only

Explanation:

• Statement 1 is incorrect: The Cassini-Huygens mission was a joint NASA-ESA mission sent to Saturn, not Venus. The Cassini orbiter studied Saturn, while the Huygens probe landed on Titan, Saturn’s largest moon.
  
  
• Statement 2 is correct: MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was the first spacecraft to orbit Mercury, providing detailed maps and data about its surface and atmosphere.
  
  
• Statement 3 is correct: Voyager 1 and 2 were launched by NASA in 1977 to explore the outer solar system. Voyager 1 has entered interstellar space, while Voyager 2 explored Uranus and Neptune.
  
  

101. With reference to Agni-IV Missile, which of the following statements is/are correct?

(UPSC CSE Pre 2014)

1. It is a surface-to-surface missile.
   
   
2. It is fueled by liquid propellant only.
   
   
3. It can deliver one-tonne nuclear warheads about 7500 km away.
   
   

Answer: (a) 1 only

Explanation:

• Statement 1 is correct: Agni-IV is a surface-to-surface intermediate-range ballistic missile (IRBM) developed by India’s DRDO (Defence Research and Development Organisation).
  
  
• Statement 2 is incorrect: Agni-IV uses a two-stage solid-fueled propulsion system, not liquid fuel.
  
  
• Statement 3 is incorrect: Agni-IV has a range of about 3500 to 4000 km, not 7500 km. The missile that can reach 7500 km would be Agni-VI (under development).
  
  

102. Consider the following diseases:

(UPSC CSE Pre 2014)

1. Diphtheria
   
   
2. Chickenpox
   
   
3. Smallpox
   
   

Which of the above diseases has/have been eradicated in India?

Answer: (b) 3 only

Explanation:

• Diphtheria (Statement 1) is not eradicated: Diphtheria still occurs in India, though vaccination through the DPT vaccine has significantly reduced its prevalence.
  
  
• Chickenpox (Statement 2) is not eradicated: Chickenpox is common, though vaccines like Varicella help prevent severe cases.
  
  
• Smallpox (Statement 3) is eradicated: Smallpox was officially eradicated globally in 1980 due to the WHO's vaccination campaign. India was declared smallpox-free in 1977.
  
  

103. In addition to fingerprint scanning, which of the following can be used in the biometric identification of a person?

(UPSC CSE Pre 2014)

1. Iris scanning
   
   
2. Retinal scanning
   
   
3. Voice recognition
   
   

Answer: (d) 1, 2, and 3

Explanation:

• Iris scanning (Statement 1) is correct: It scans the unique pattern in a person’s iris (colored part of the eye) for identification.
  
  
• Retinal scanning (Statement 2) is correct: It analyzes the unique pattern of blood vessels in the retina.
  
  
• Voice recognition (Statement 3) is correct: It identifies a person based on their unique vocal characteristics.
  
  

All three methods are used in biometric security systems, including Aadhaar authentication in India.

104. With reference to technology for solar power production, consider the following statements:

(UPSC CSE Pre 2014)

1. 'Photovoltaics' is a technology that generates electricity by direct conversion of light into electricity, while 'Solar Thermal' is a technology that utilizes the Sun's rays to generate heat, which is further used in electricity generation.
   
   
2. Photovoltaics generates Alternating Current (AC), while Solar Thermal generates Direct Current (DC).
   
   
3. India has a manufacturing base for Solar Thermal technology but not for photovoltaics.
   
   

Answer: (a) 1 only

Explanation:

• Statement 1 is correct: Photovoltaic (PV) technology directly converts sunlight into electricity using solar cells. Solar thermal technology uses concentrated solar power (CSP) to generate heat, which is then converted into electricity.
  
  
• Statement 2 is incorrect: Photovoltaic systems generate Direct Current (DC), not Alternating Current (AC). DC is later converted to AC using an inverter.
  
  
• Statement 3 is incorrect: India has a growing manufacturing base for both solar photovoltaic (PV) panels and solar thermal systems. India is one of the world's largest producers of solar PV modules.

05. Consider the following diseases:

(UPSC CSE Pre 2014)

1. Diphtheria
   
   
2. Chickenpox
   
   
3. Smallpox
   
   

Which of the above diseases has/have been eradicated in India?

Answer: (b) 3 only

Explanation:

• Diphtheria (Statement 1) is not eradicated: Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae. While cases have reduced due to vaccination (DPT vaccine), it still occurs in India, especially among unvaccinated individuals.
  
  
• Chickenpox (Statement 2) is not eradicated: Chickenpox, caused by the Varicella-zoster virus, is still prevalent in India, although vaccines help reduce its severity.
  
  
• Smallpox (Statement 3) is eradicated: Smallpox was eradicated globally in 1980 due to WHO's vaccination efforts. India was declared smallpox-free in 1977.
  
  

106. Which of the following diseases can be transmitted from one person to another through tattooing?

(UPSC CSE Pre 2013)

1. Chikungunya
   
   
2. Hepatitis B
   
   
3. HIV-AIDS
   
   

Answer: (b) Only 2 and 3

Explanation:

• Chikungunya (Statement 1) is incorrect: Chikungunya is a mosquito-borne viral disease and is not transmitted through tattooing.
  
  
• Hepatitis B (Statement 2) is correct: Hepatitis B is a blood-borne viral infection that can be transmitted through contaminated needles, including those used in tattooing.
  
  
• HIV-AIDS (Statement 3) is correct: HIV can be transmitted through infected needles used in tattooing, as the virus spreads via blood and bodily fluids.
  
  

Thus, only Hepatitis B and HIV-AIDS can be transmitted through tattooing.

107. Recombinant DNA Technology (Genetic Engineering) allows genes to be transferred

(UPSC CSE Pre 2013)

1. Across different species of plants.
   
   
2. From animals to plants.
   
   
3. From microorganisms to higher organisms.
   
   

Answer: (d) All of these

Explanation:

Recombinant DNA technology (Genetic Engineering) allows genes from one organism to be introduced into another, even across species barriers.

• Statement 1 is correct: Genes can be transferred across different plant species. Example: Golden rice, which contains genes from maize and a soil bacterium (Erwinia).
  
  
• Statement 2 is correct: Genes from animals can be transferred to plants. Example: Human insulin gene has been introduced into bacteria for large-scale insulin production.
  
  
• Statement 3 is correct: Genes from microorganisms can be inserted into higher organisms. Example: The Bt gene from Bacillus thuringiensis has been inserted into plants to make Bt cotton resistant to pests.
  
  

Thus, all three statements are correct.

108. Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to

(UPSC CSE Pre 2013)

1. Resist drought and increase absorptive area.
   
   
2. Tolerate extremes of pH.
   
   
3. Resist disease infestation.
   
   

Answer: (d) All of these

Explanation:

Mycorrhiza refers to a symbiotic association between fungi and plant roots, which enhances plant growth and survival in degraded environments.

• Statement 1 is correct: Mycorrhiza increases the root surface area, improving water and nutrient absorption, helping plants resist drought.
  
  
• Statement 2 is correct: Mycorrhiza helps plants tolerate extreme soil pH levels by improving nutrient uptake and modifying soil conditions.
  
  
• Statement 3 is correct: Mycorrhiza protects plants from diseases by enhancing immunity and competing with harmful pathogens in the soil.
  
  

Thus, all three statements are correct.