UNIVERSE & THE EVOLUTION OF EARTH

1. In the Northern Hemisphere, when does the longest day of the year typically occur?
 [UPSC CSE Prelims 2022]

(a) First half of June
(b) Second half of June
(c) First half of July
(d) Second half of July

Correct Answer: (b) Second half of June

Explanation:
 The longest day of the year in the Northern Hemisphere is known as the Summer Solstice, which usually occurs on June 20, 21, or 22. This is the time when the Sun is directly overhead at 23.5° North latitude (Tropic of Cancer), leading to the maximum amount of daylight.

For example, in 2021, the longest day in the Northern Hemisphere was on June 21.

Other related astronomical events include:

• Winter Solstice (December 21 or 22) – Shortest day of the year in the Northern Hemisphere.
• Vernal Equinox (March 20 or 21) – Equal day and night.
• Autumnal Equinox (September 22 or 23) – Equal day and night.

2. Consider the following statements regarding the effect of clouds on Earth's temperature:
 [UPSC CSE Prelims 2022]

1. High-altitude clouds primarily reflect solar radiation, leading to a cooling effect on the Earth's surface.
2. Low-altitude clouds have a strong ability to absorb infrared radiation emitted from the Earth's surface, thereby causing a warming effect.
   
   

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

Correct Answer: (d) Neither 1 nor 2

Explanation:
 The heating or cooling effect of clouds depends on multiple factors, including their altitude, thickness, and composition:

• Statement 1 is incorrect: Low, thick clouds (such as stratus and cumulus clouds) mainly reflect incoming solar radiation, leading to a cooling effect rather than warming.
• Statement 2 is incorrect: High, thin clouds (such as cirrus clouds) primarily allow sunlight to pass through but trap outgoing infrared radiation, radiating it back to Earth. This results in a warming effect rather than cooling.

Thus, since both statements do not accurately describe the impact of clouds, the correct answer is (d) Neither 1 nor 2.

3. What is the difference between asteroids and comets?
[UPSC CSE Prelims 2014]

1. Asteroids are small rocky planetoids, while comets are formed of frozen gases held together by rocky and metallic material.
2. Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly between Venus and Mercury.
3. Comets show a perceptible glowing tail, while asteroids do not.

Which of the statements given above is/are correct?

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

Correct Answer: (b) 1 and 3 only

Explanation:

• Statement 1 is correct: Asteroids are small, rocky objects that orbit the Sun, primarily composed of metals and silicate materials. Comets, on the other hand, are made up of frozen gases, rock, and dust, often described as "dirty snowballs."
• Statement 2 is incorrect: Asteroids are mostly found in the asteroid belt between Mars and Jupiter. However, comets are not confined to a specific region; they originate primarily from the Kuiper Belt (beyond Neptune) and the Oort Cloud (a distant spherical shell surrounding the Solar System). They are not concentrated between Venus and Mercury.
• Statement 3 is correct: Comets develop a glowing tail when they approach the Sun due to the sublimation of their icy components, whereas asteroids do not have tails.

GEOMORPOLOGY

1. Which one of the following is a part of the Congo Basin? [UPSC CSE Pre 2023]

(a) Cameroon
(b) Nigeria
(c) South Sudan
(d) Uganda

Solution: (a)

Explanation: The Congo Basin is a vast region in Central Africa, encompassing multiple countries. It is primarily characterized by the Congo Rainforest, the second-largest rainforest in the world. The Congo Basin spans across six countries—Cameroon, Central African Republic, Democratic Republic of the Congo, Republic of the Congo, Equatorial Guinea, and Gabon.

• Nigeria (b) is in West Africa and not part of the Congo Basin.
• South Sudan (c) is in East-Central Africa and does not fall within the basin.
• Uganda (d) is in East Africa and is close to the eastern edge of the basin but does not lie entirely within it.

2. With reference to the Earth's atmosphere, which one of the following statements is correct? [UPSC CSE Pre 2023]

(a) The total amount of insolation received at the equator is roughly about 10 times that received at the poles.
(b) Infrared rays constitute roughly two-thirds of insolation.
(c) Infrared waves are largely absorbed by water vapor that is concentrated in the lower atmosphere.
(d) Infrared waves are a part of the visible spectrum of electromagnetic waves of solar radiation.

Solution: (c)

Explanation:

• (c) is correct. Water vapor is a potent absorber of infrared radiation, particularly in certain wavelength bands. In the lower atmosphere, where water vapor concentration is relatively higher, it absorbs a significant amount of infrared radiation emitted by the Earth's surface, contributing to the greenhouse effect.
• (a) is incorrect. While the equator does receive more direct sunlight than the poles, the actual difference in insolation is not as large as ten times.
• (b) is incorrect. Insolation includes various electromagnetic waves, and infrared does not constitute two-thirds of the total.
• (d) is incorrect. Infrared waves lie just beyond the red end of the visible spectrum and are not part of visible light.

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

1. In a seismograph, P waves are recorded earlier than S waves.
2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation, whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.

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. P waves (Primary waves) are the fastest seismic waves and are recorded first on a seismograph. They can move through solids, liquids, and gases.
• Statement 2 is correct. P waves are longitudinal waves, meaning particle motion occurs parallel to wave propagation. In contrast, S waves (Secondary waves) are transverse waves, causing particles to move perpendicularly (up and down) to the direction of wave propagation.

4. With reference to water on Earth, consider the following statements: [UPSC CSE Pre 2021]

1. The amount of water in rivers and lakes is more than the amount of groundwater.
2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater.

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. Of the total freshwater, 69% resides in glaciers, 30% underground, and less than 1% in lakes, rivers, and swamps. Thus, the amount of water in rivers and lakes is less than that of groundwater.
• Statement 2 is correct. Polar ice caps and glaciers contain more water than groundwater.

5. Consider the following statements: [UPSC CSE Pre 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

Solution: (c)

Explanation:

• Statement 1 is correct. Paleomagnetism studies show that Earth's magnetic field reverses direction periodically.
• Statement 2 is incorrect. Earth's early atmosphere had no oxygen; it mainly contained methane, carbon dioxide, water vapor, nitrogen, and ammonia.
• Statement 3 is correct. Early photosynthetic organisms like cyanobacteria significantly altered Earth's atmosphere by releasing oxygen.

6. Which of the following phenomena might have influenced the evolution of organisms? [UPSC CSE Pre 2014]

1. Continental drift
2. Glacial cycles

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

Solution: (c)

Explanation: Both continental drift and glacial cycles have significantly influenced the evolution of organisms by affecting climate patterns and geographical distribution.

7. Which one of the following pairs is correctly matched? [UPSC CSE Pre 2014]

Geographical Feature - Region
(a) Abyssinian Plateau - Arabia
(b) Atlas Mountains - North-Western Africa
(c) Guiana Highlands - South-Western Africa
(d) Okavango Basin - Patagonia

Solution: (b)

Explanation:

• The Atlas Mountains are located in North-Western Africa (correct match).
• The Abyssinian Plateau is in Ethiopia, not Arabia.
• The Guiana Highlands are in South America, not Africa.
• The Okavango Basin is in South-Western Africa, not Patagonia.

8. Consider the following: [UPSC CSE Pre. 2014]

Electromagnetic radiation

Geothermal energy

Gravitational force

Plate movements

Rotation of the Earth

Revolution of the Earth

Which of the above are responsible for bringing dynamic changes on the surface of the Earth? 

(a) 1, 2, 3, and 4 only

(b) 1, 3, 5, and 6 only

(c) 2, 4, 5, and 6 only

(d) 1, 2, 3, 4, 5, and 6 

Solution: (d)

Explanation:

All the given factors contribute to dynamic changes on the Earth’s surface. The transformation from potential to kinetic energy results in various natural phenomena. 

Electromagnetic radiation – The Sun’s radiation provides heat and energy, driving life on Earth, precipitation, and weathering of surfaces.

Geothermal energy – Heat from within the Earth leads to volcanic activity, melting of ice caps, and tectonic movements.

Gravitational force – It maintains stability in the solar system, causes oceanic tides, and contributes to erosion and deposition.

Plate movements – The shifting of tectonic plates results in the formation of islands, mountains, earthquakes, and volcanoes.

Rotation of the Earth – Causes day and night, influences pressure variations, drives wind patterns, and impacts ocean currents via the Coriolis effect.

Revolution of the Earth – Responsible for seasonal changes, which, in turn, affect erosion, weathering, and overall landscape modification.

Thus, all six factors contribute to changes on Earth's surface, making option (d) the correct answer.

OCEANOGRAPHY

1. Consider the following statements:

[UPSC CSE Pre. 2023]

Statement-I: The temperature contrast between continents and oceans is greater during summer than in winter.
 Statement-II: The specific heat of water is more than that of the land surface.

Which one of the following is correct?

(a) Both Statement-I and Statement-II are correct, and Statement-II is the correct explanation for Statement-I.
 (b) Both Statement-I and Statement-II are correct, but Statement-II is not the correct explanation for Statement-I.
 (c) Statement-I is correct, but Statement-II is incorrect.
 (d) Statement-I is incorrect, but Statement-II is correct.

Solution: (d)

Explanation:

• Statement-I is incorrect – The temperature contrast between continents and oceans is actually greater during winter than in summer.
• Statement-II is correct – Water has a higher specific heat capacity than land, meaning it requires more heat to raise its temperature. This property helps regulate temperature changes, causing slower heating and cooling of oceans compared to land.

2. With reference to Ocean Mean Temperature (OMT), consider the following statements:

[UPSC CSE Pre. 2020]

1. OMT is measured up to a depth of the 26°C isotherm, which is 129 meters in the southwestern Indian Ocean during January-March.

2. OMT collected during January-March can be used to assess whether the amount of rainfall in the monsoon will be more or less than a certain long-term mean.

Select the correct answer using the code below:
 (a) 1 only
 (b) 2 only
 (c) Both 1 and 2
 (d) Neither 1 nor 2

Solution: (b)

Explanation:

• Statement 1 is incorrect – While OMT is measured up to the 26°C isotherm, its depth varies from 50-100 meters, and during January-March, it is around 59 meters in the southwestern Indian Ocean.
• Statement 2 is correct – OMT data collected in January-March helps predict monsoon rainfall patterns by assessing heat content in the ocean.

3. Consider the following statements about coral reefs:

[UPSC CSE Pre. 2018]

1. Most of the world's coral reefs are found in tropical waters.

2. More than one-third of the world’s coral reefs are located in Australia, Indonesia, and the Philippines.

3. Coral reefs host a greater number of animal phyla than tropical rainforests.

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

Solution: (d)

Explanation:

• Statement 1 is correct – Coral reefs thrive in tropical shallow waters (typically less than 50 meters deep).
• Statement 2 is correct – Over one-third of the world's corals are found in Australia (17%), Indonesia (16%), and the Philippines (9%).
• Statement 3 is correct – Coral reefs support over 25,000 species from 32 out of 33 known animal phyla, far more than tropical rainforests.

4. Tides occur in the oceans and seas due to which among the following?

[UPSC CSE Pre. 2015]

1. Gravitational force of the Sun

2. Gravitational force of the Moon

3. Centrifugal force of the Earth

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

Solution: (d)

Explanation:

• The gravitational pull of the Moon and Sun causes tides.
• The centrifugal force due to Earth’s rotation also influences tidal bulges.
• The Moon’s gravity has a stronger effect than the Sun, leading to high and low tides.

5. Which of the following regions have coral reefs?

[UPSC CSE Pre. 2014]

1. Andaman and Nicobar Islands

2. Gulf of Kachchh

3. Gulf of Mannar

4. Sunderbans

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

Solution: (a)

Explanation:

• Coral reefs require clear, warm, and saline waters to thrive.
• Coral reefs in India are found in:
  • Gulf of Mannar
  • Gulf of Kachchh
  • Andaman & Nicobar Islands
  • Lakshadweep Islands
• Sundarbans (Option 4) does not have coral reefs due to its high freshwater inflow.

6. The most important fishing grounds in the world are found in regions where:

[UPSC CSE Pre. 2014]

(a) Warm and cold atmospheric currents meet
 (b) Rivers drain large amounts of freshwater into the sea
 (c) Warm and cold oceanic currents meet
 (d) The continental shelf is undulating

Solution: (c)

Explanation:

• The meeting of warm and cold ocean currents creates upwelling zones, rich in plankton, which support large fish populations.
• Example: Grand Banks (North America), where the cold Labrador Current meets the warm Gulf Stream, making it one of the world's richest fishing grounds.

CLIMATIOLOGY

1. Consider the following statements:

• The troposphere is thicker at the equator than at the poles.

• The magnitude of the Coriolis force is determined by the wind speed.

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

Detailed Explanation:

• Statement 1: The troposphere is thicker at the equator than at the poles.
  
  
  • The troposphere is the lowest layer of the Earth's atmosphere, where weather phenomena occur.
  • The thickness of the troposphere varies with latitude due to differences in temperature and convection.
  • At the equator, due to intense solar heating, there is more convection, pushing the troposphere to 16-18 km in height.
  • At the poles, where solar heating is weak, the troposphere is much thinner, around 8-10 km in height.
  • This variation is due to thermal expansion—warmer air rises higher, while colder air contracts, making the troposphere thinner at the poles.
  • Thus, this statement is correct.
• Statement 2: The magnitude of the Coriolis force is determined by the wind speed.
  
  
  • The Coriolis force is the deflection of moving objects (such as winds and ocean currents) due to Earth's rotation.
  • It is proportional to both:
    1. The speed of the moving object (wind, ocean current, etc.).
    2. The sine of the latitude (zero at the equator and maximum at the poles).
  • This means that faster winds experience a stronger Coriolis force, which causes them to deflect more.
  • Therefore, this statement is also correct.

2. Consider the following statements:

• The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.

• Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long-wave radiation.

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: (b) 2 only

Detailed Explanation:

• Statement 1: The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.
  
  
  • The atmosphere is not directly heated by incoming solar radiation.
  • Solar radiation (short-wave radiation) from the Sun passes through the atmosphere and is absorbed by the Earth's surface.
  • The Earth then reradiates heat in the form of infrared radiation (long-wave radiation).
  • This long-wave radiation is absorbed by greenhouse gases (CO₂, methane, water vapor, etc.), warming the atmosphere.
  • This process is called the Greenhouse Effect, and it is why terrestrial radiation plays a much bigger role in heating the atmosphere than direct solar radiation.
• Statement 2: Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long-wave radiation.
  
  
  • Greenhouse gases like carbon dioxide (CO₂), methane (CH₄), and water vapor absorb infrared radiation emitted by the Earth's surface.
  • This absorbed heat is then reradiated in all directions, warming the atmosphere and Earth's surface, trapping heat and leading to global warming.
  • This is the fundamental mechanism behind climate change.

3. Consider the following statements:

• The Coriolis force is zero at the equator.

• The Coriolis force increases with increasing latitude.

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

Detailed Explanation:

• Statement 1: The Coriolis force is zero at the equator.
  
  
  • The Coriolis force depends on the rotation of the Earth and acts perpendicular to the direction of motion of moving air masses.
  • The force is given by the equation: Coriolis Force=2×Earth′s Rotation Rate×Velocity of Object×sin⁡(Latitude)Coriolis\ Force = 2 \times Earth's\ Rotation\ Rate \times Velocity\ of\ Object \times \sin (Latitude)Coriolis Force=2×Earth′s Rotation Rate×Velocity of Object×sin(Latitude)
  • At the equator (latitude = 0°), sin(0°) = 0, so the Coriolis force vanishes completely.
  • This means winds and ocean currents at the equator do not experience any Coriolis deflection.
• Statement 2: The Coriolis force increases with increasing latitude.
  
  
  • The Coriolis force is proportional to the sine of the latitude (sin θ), which increases as we move towards the poles.
  • At higher latitudes, the component of Earth's rotation perpendicular to the surface is greater, resulting in stronger Coriolis effects.
  • It is zero at 0° (equator), moderate at 30°-60°, and strongest at 90° (poles).
  • This explains why large cyclonic systems like hurricanes and typhoons are absent near the equator but prevalent in mid and high latitudes.

4. Consider the following trees: (UPSC CSE Pre 2023)

1. Jackfruit (Artocarpus heterophyllus)
2. Mahua (Madhuca indica)
3. Teak (Tectona grandis)

How many of the above are deciduous trees?

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

Solution: (b) Only two
 Explanation:

• Jackfruit is an evergreen tree.
• Mahua and Teak are deciduous trees.

5. Consider the following statements: (UPSC CSE Pre 2023)

Statement-I: The soil in tropical rain forests is rich in nutrients.
 Statement-II: The high temperature and moisture of tropical rain forests cause dead organic matter in the soil to decompose quickly.

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 is the correct explanation for Statement-I.
 (b) Both Statement-I and Statement-II are correct, but Statement-II is not the correct explanation for Statement-I.
 (c) Statement-I is correct, but Statement-II is incorrect.
 (d) Statement-I is incorrect, but Statement-II is correct.

Solution: (d) Statement-I is incorrect but Statement-II is correct.
 Explanation:

• Tropical rainforest soil is nutrient-poor due to its acidic nature and heavy rainfall, which causes leaching.
• Decomposition is rapid due to high temperatures and moisture, supporting Statement-II.

6. Consider the following statements: (UPSC CSE Pre 2021)

1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections, owing to the influence of trade winds.
2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections.

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) Both 1 and 2
 Explanation:

• Statement 1 is correct: Trade winds transport warm water westward in the tropical oceans, making the western sections warmer than the eastern ones.
• Statement 2 is correct: Westerlies move warm equatorial waters toward the eastern sections of temperate oceans.

 7. "Leaf litter decomposes faster than in any other biome and as a result, the soil surface is often almost bare. Apart from trees, the vegetation is largely composed of plant forms that reach up into the canopy vicariously, by climbing the trees or growing as epiphytes, rooted on the upper branches of trees." (UPSC CSE Pre 2021)

This is the most likely description of:

(a) Coniferous forest
 (b) Dry deciduous forest
 (c) Mangrove forest
 (d) Tropical rain forest

Solution: (d) Tropical rain forest
 Explanation:

• Rapid decomposition occurs due to the hot and humid climate.
• Epiphytes and climbing plants grow abundantly due to intense competition for sunlight.

8. The vegetation of the savannah consists of grassland with scattered small trees, but extensive areas have no trees. The forest development in such areas is generally kept in check by one or more or a combination of some conditions. (UPSC CSE Pre 2021)

Which of the following are such conditions?

1. Burrowing animals and termites

2. Fire

3. Grazing herbivores

4. Seasonal rainfall

5. Soil properties

Select the correct answer using the code given below:

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

Solution: (c) 2, 3, and 4
 Explanation:

• Fire (2) frequently occurs in savannas and prevents large-scale tree growth.
• Grazing herbivores (3) such as elephants and giraffes feed on tree saplings, limiting forest expansion.
• Seasonal rainfall (4) leads to extended dry periods, preventing the development of dense forests.
• Burrowing animals and termites (1) do not significantly limit tree growth.
• Soil properties (5) in savannas are generally deep and do not prevent tree growth.

9. Consider the following statements: (UPSC CSE Pre 2020)

1. Jet streams occur in the Northern Hemisphere only.
2. Only some cyclones develop an eye.
3. The temperature inside the eye of a cyclone is nearly 10°C lower than that of the surroundings.

Which of the statements given above is/are correct?

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

Solution: (c) 2 only
 Explanation:

• Statement 1 is incorrect: Jet streams occur in both hemispheres. They are high-altitude westerly wind systems found at 6-14 km altitude with speeds up to 450 km/h.
• Statement 2 is correct: Only tropical cyclones develop a well-defined eye.
• Statement 3 is incorrect: The eye of a cyclone is warmer than the surroundings due to descending air and low pressure.

10.  Consider the following statements: (UPSC CSE Pre 2020)

1. High clouds primarily reflect solar radiation and cool the surface of the Earth.

2. Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause a warming effect.

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: (d) Neither 1 nor 2
 Explanation:

• The impact of clouds on surface temperature depends on factors such as altitude, thickness, and the composition of cloud particles.
• Statement 1 is incorrect: Low, thick clouds primarily reflect solar radiation, which results in a cooling effect on the Earth's surface rather than warming.
• Statement 2 is incorrect: High, thin clouds primarily allow incoming solar radiation to pass through while simultaneously trapping outgoing infrared radiation from the Earth. This trapped heat is re-radiated back downward, leading to a warming effect rather than a cooling one.

11. Why are dewdrops not formed on a cloudy night? (UPSC CSE Pre 2019)

(a) Clouds absorb the radiation released from the Earth's surface.
 (b) Clouds reflect back the Earth's radiation.
 (c) The Earth's surface would have a low temperature on cloudy nights.
 (d) Clouds deflect the blowing wind to ground level.

Solution: (b) Clouds reflect back the Earth's radiation.
 Explanation:

• Dew forms when moisture condenses onto cooler surfaces like grass, leaves, or stones. This condensation occurs when the temperature drops to the dew point, which is the temperature at which air becomes saturated with moisture.
• Ideal conditions for dew formation include clear skies, calm air, high relative humidity, and long, cold nights.
• On clear nights, the Earth's surface cools significantly due to longwave radiation emission, leading to dew formation.
• However, on cloudy nights, clouds reflect back the Earth's radiation, preventing the ground from cooling enough to reach the dew point. This inhibits the formation of dewdrops.

12. In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (UPSC CSE Pre 2015)

(a) Sea surface temperatures are low.
 (b) Inter-tropical Convergence Zone seldom occurs.
 (c) Coriolis force is too weak.
 (d) Absence of land in those regions.

Solution: (b) Inter-tropical Convergence Zone seldom occurs.
 Explanation:

• Cyclones require the Inter-Tropical Convergence Zone (ITCZ) to shift significantly away from the equator, which allows the Coriolis force to influence storm rotation.
• In the South Atlantic and South-Eastern Pacific, the ITCZ remains close to the equator or northward, meaning there isn’t enough broad convergence of air masses to support cyclone formation.
• Additionally, the Coriolis force near the equator is weak, making it difficult for cyclones to develop and sustain rotation.

13. What explains the eastward flow of the equatorial counter-current? (UPSC CSE Pre 2015)

(a) The Earth's rotation on its axis.
 (b) Convergence of the two equatorial currents.
 (c) Difference in salinity of water.
 (d) Occurrence of the belt of calm near the equator.

Solution: (b) Convergence of the two equatorial currents.
 Explanation:

• There are two equatorial currents flowing from east to west: the North Equatorial Current and the South Equatorial Current.
• Some of the water from these currents gets deflected back toward the equator, piling up near Brazil.
• This accumulation of water leads to the Equatorial Counter Current, which flows opposite to the main equatorial currents (i.e., from west to east).

14. Consider the following statements: (UPSC CSE Pre 2015)

1. The winds that blow between 30°N and 60°S latitudes throughout the year are known as westerlies.
2. The moist air masses that cause winter rains in the northwestern region of India are part of the westerlies.

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) 2 only
 Explanation:

• Statement 1 is incorrect: The Westerlies are winds that blow between 30°-60° in both hemispheres. The given latitude 30°N to 60°S is incorrect, as the correct range is 30°S to 60°S in the Southern Hemisphere.
• Statement 2 is correct: The Western Disturbances originate over the Mediterranean Sea and are carried toward Northwestern India by Westerly Jet Streams, bringing winter rainfall.

15. "Each day is more or less the same. The morning is clear and bright with a sea breeze; as the sun climbs high, heat mounts up, dark clouds form, then rain comes with thunder and lightning. But the rain is soon over." (UPSC CSE Pre 2015)

Which of the following regions is described in the above passage?

(a) Savannah
 (b) Equatorial
 (c) Monsoon
 (d) Mediterranean

Solution: (b) Equatorial
 Explanation:

• Equatorial regions experience hot, humid weather with little seasonal variation.
• Due to intense solar heating, the air rises, cools, and condenses, leading to daily convectional rainfall in the afternoon, often accompanied by thunder and lightning.

16. Variations in the length of daytime and nighttime from season to season are due to: (UPSC CSE Pre 2014)

(a) The Earth's rotation on its axis.
 (b) The Earth's revolution around the Sun in an elliptical manner.
 (c) The latitudinal position of the place.
 (d) The revolution of the Earth on a tilted axis.

Solution: (d) The revolution of the Earth on a tilted axis.
 Explanation:

• The Earth's 5° axial tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year.
• When the North Pole tilts toward the Sun, the Northern Hemisphere experiences summer with longer days.
• Conversely, when the South Pole tilts toward the Sun, the Southern Hemisphere has summer, while the Northern Hemisphere has winter with shorter days.

17. On planet Earth, most of the freshwater exists as ice caps and glaciers. Out of the remaining freshwater, the largest proportion: (UPSC CSE Pre 2014)

(a) Is found in the atmosphere as moisture and clouds.
 (b) Is found in freshwater lakes and rivers.
 (c) Exists as groundwater.
 (d) Exists as soil moisture.

Solution: (c) Exists as groundwater.
 Explanation:

• Of all freshwater, 69% is stored in glaciers and ice caps, while 30% is groundwater.
• Less than 1% of freshwater exists in lakes, rivers, and swamps.

18. Which of the following leaf modifications occur in desert areas to inhibit water loss? (UPSC CSE Pre 2014)

1. Hard and waxy leaves
2. Tiny leaves or no leaves
3. Thorns instead of leaves

Solution: (d) 1, 2, and 3
 Explanation:

• Hard, waxy leaves reduce evaporation.
• Tiny leaves or no leaves minimize transpiration.
• Thorns replace leaves in some plants (e.g., cacti) to further conserve water. 

19. The annual range of temperature in the interior of the continents is high as compared to coastal areas. What is/are the reason(s)? (UPSC CSE Pre 2014)

1. Thermal difference between land and water.
2. Variation in altitude between continents and oceans.
3. Presence of strong winds in the interior.
4. Heavy rains in the interior as compared to coasts.

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

Solution: (a) 1 only
 Explanation:

• The annual range of temperature refers to the difference between the warmest and coldest months of the year at a given location.
• Statement 1 is correct: Land heats up and cools down faster than water due to differences in heat capacity. Coastal areas experience moderating influence from the sea, whereas inland locations heat up significantly in summer and cool rapidly in winter. This results in a higher temperature range in the interior of continents.
• Statement 2 is incorrect: Altitude primarily affects daily temperature variations and the mean temperature but has minimal influence on the annual range of temperature.
• Statement 3 is incorrect: Strong winds are typically more prevalent near coasts rather than deep inland. Coastal winds help regulate temperature, but their absence in interiors does not directly cause a high temperature range.
• Statement 4 is incorrect: Interiors of continents generally receive lower rainfall than coastal regions because moisture-laden winds lose most of their moisture before reaching inland areas.

20. Which of the following is/are unique characteristic(s) of equatorial forests? (UPSC CSE Pre 2014)

1. Presence of tall, closely set trees with crowns forming a continuous canopy.

2. Coexistence of a large number of species.

3. Presence of numerous varieties of epiphytes.

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: (d) 1, 2, and 3
 Explanation:

• Statement 1 is correct: Equatorial forests, also known as tropical rainforests, have a dense, multilayered structure with tall trees growing closely together. The upper layer, known as the canopy, is formed by interlocking branches of trees, blocking most sunlight from reaching the forest floor.
• Statement 2 is correct: These forests support the greatest biodiversity on Earth. Even though they cover less than 2% of the Earth's surface, they house over 50% of all plant and animal species due to the warm, humid, and stable climate.
• Statement 3 is correct: The presence of epiphytes (plants that grow on other plants for support but do not extract nutrients from them) is a key feature of equatorial forests. Epiphytes include orchids, ferns, and bromeliads, and they grow on canopy trees to access sunlight.

21. "Climate is extreme, rainfall is scanty, and the people used to be nomadic herders." (UPSC CSE Pre 2014)

This statement best describes which of the following regions?

(a) African Savannah
 (b) Central Asian Steppe
 (c) North American Prairie
 (d) Siberian Tundra

Solution: (b) Central Asian Steppe
 Explanation:

• The Central Asian Steppe is a vast, dry, grassy plain that extends across Kazakhstan, Mongolia, and parts of Russia and China.
• These temperate grasslands experience a continental climate with extreme temperature variations – summers can reach 45°C, while winters can drop to -55°C.
• Rainfall is low (25-50 cm annually), making agriculture difficult. Instead, the region is historically known for nomadic herding of cattle, goats, camels, horses, and sheep.
• Due to the harsh climate, trees are scarce, and the Kirghiz, Mongols, and other nomadic groups have traditionally inhabited this region.

22. During a thunderstorm, the thunder in the skies is produced by: (UPSC CSE Pre 2014)

1. Meeting of cumulonimbus clouds in the sky.

2. Lightning that separates the nimbus clouds.

3. Violent upward movement of air and water particles.

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

Solution: (d) None of the above produces the thunder
 Explanation:

• Thunder is not caused by cloud collisions, lightning separating clouds, or moving air particles. Instead, it occurs due to the rapid expansion of heated air surrounding a lightning bolt.
• Formation of thunder:
  • When lightning occurs, it instantly heats the surrounding air to temperatures around 30,000°C (five times hotter than the Sun's surface).
  • This extreme heating causes the air to expand explosively, creating a shockwave that we hear as thunder.
  • The time delay between lightning and thunder is due to the difference in speed – light travels almost instantly, but sound moves slower (about 343 m/s in air).
• Why are the given statements incorrect?
  • Statement 1 is incorrect: Cumulonimbus clouds are responsible for thunderstorms, but their meeting does not directly produce thunder.
  • Statement 2 is incorrect: Lightning does not separate clouds; it results from electrical charge accumulation within clouds.
  • Statement 3 is incorrect: Though thunderstorms involve strong updrafts of air and water droplets, these do not create the sound of thunder.

 INDIA PHYSICAL ENVIRONMENT

1. Consider the following statements: (UPSC CSE Pre 2023)

1. Jhelum River passes through Wular Lake.
2. Krishna River directly feeds Kolleru Lake.
3. Meandering of Gandak River formed Kanwar Lake.

How many of the statements given above are correct?
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (a)
 Exp) Option (a) is the correct answer.

• Statement 1 is correct: The Jhelum River, originating from Verinag in Jammu and Kashmir, flows through Srinagar and Wular Lake before entering Pakistan via a deep gorge. It later joins the Chenab River.
• Statement 2 is incorrect: Kolleru Lake acts as a flood-balancing reservoir for the Krishna and Godavari rivers. However, it is not directly fed by the Krishna River but by seasonal streams such as Budameru and Tammileru.
• Statement 3 is correct: Kanwar Lake, once a thriving freshwater oxbow lake in Bihar, was formed due to the meandering of the Gandak River, a tributary of the Ganga.

2. Which one of the following is the best example of repeated falls in sea level, giving rise to present-day extensive marshland? (UPSC CSE Pre 2023)

(a) Bhitarkanika Mangroves
 (b) Marakkanam Salt Pans
 (c) Naupada Swamp
 (d) Rann of Kutch

Solution: (d)
 Exp) Option (d) is the correct answer.

• Bhitarkanika Mangroves (Odisha) are primarily influenced by riverine systems and tidal fluctuations rather than a fall in sea level.
• Marakkanam Salt Pans (Tamil Nadu) are artificially created for salt production and do not result from sea-level changes.
• Naupada Swamp (Odisha) is a freshwater wetland influenced by seasonal rainwater and river inflow.
• Rann of Kutch (Gujarat) is the best example of sea-level fluctuations. Historically, it was part of the Arabian Sea, but geological changes caused a gradual regression, leading to the formation of a vast salt marsh.

3. Consider the following statements: (UPSC CSE Pre 2023)

1. Amarkantak Hills are at the confluence of the Vindhya and Sahyadri Ranges.
2. Biligirirangan Hills constitute the easternmost part of the Satpura Range.
3. Seshachalam Hills constitute the southernmost part of the Western Ghats.

How many of the statements given above are correct?
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (d)
 Exp) Option (d) is the correct answer.

• Statement 1 is incorrect: Amarkantak is located at the meeting point of the Vindhya and Satpura ranges, along with the Maikal Hills, and is not associated with the Sahyadri (Western Ghats).
• Statement 2 is incorrect: The Biligirirangan Hills (BR Hills) are located in Karnataka and form an ecological bridge between the Eastern and Western Ghats. They are not part of the Satpura Range.
• Statement 3 is incorrect: The Seshachalam Hills, also known as the Tirumala Hills, are part of the Eastern Ghats in Andhra Pradesh, not the Western Ghats.

4. Gandikota canyon of South India was created by which one of the following rivers? (UPSC CSE Pre 2022)

(a) Manjira
 (b) Pennar
 (c) Cauvery
 (d) Tungabhadra

Solution: (b)
 Exp) Option (b) is the correct answer.

• The Pennar River eroded the granite rocks near Gandikota in Andhra Pradesh, creating a deep valley.
• Gandikota is often referred to as the "Grand Canyon of India" due to its spectacular gorge formations.

5. Consider the following pairs: (UPSC CSE Pre 2022)

Peak	Mountain Range
1. Namcha Barwa	Garhwal Himalaya
2. Nanda Devi	Kumaon Himalaya
3. Nokrek	Sikkim Himalaya

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

Solution: (b)
 Exp) Option (b) is the correct answer.

• Pair 1 is incorrect: Namcha Barwa is not in the Garhwal Himalayas. It is located at the easternmost edge of the Himalayas in Arunachal Pradesh, near the U-turn of the Brahmaputra River.
• Pair 2 is correct: Nanda Devi is part of the Kumaon Himalayas in Uttarakhand. It is India's second-highest peak and the highest entirely within the country.
• Pair 3 is incorrect: Nokrek is not in the Sikkim Himalayas. It is the highest peak in the West Garo Hills of Meghalaya.

6. With reference to the Indus River system, which one of the following rivers joins the Indus directly? (UPSC CSE Pre 2021)

(a) Chenab
 (b) Jhelum
 (c) Ravi
 (d) Sutlej

Solution: (d)
 Exp) Option (d) is the correct answer.

• Chenab joins the Sutlej in Pakistan.
• Jhelum joins the Chenab near Jhang in Pakistan.
• Ravi joins the Chenab near Sarai Sidhu.
• Sutlej is the only river that joins the Indus directly, a few kilometers above Mithankot in Pakistan.

7. With reference to India, Didwana, Kuchaman, Sargol, and Khatu are the names of: (UPSC CSE Pre 2021)

(a) Glaciers
 (b) Mangrove areas
 (c) Ramsar sites
 (d) Saline lakes

Solution: (d)
 Exp) Option (d) is the correct answer.

• Didwana, Kuchaman, Sargol, and Khatu are all saline lakes located in Rajasthan.
• Didwana Lake is a famous saltwater lake in the Nagaur district of Rajasthan.
• Kuchaman Lake is also in Nagaur, known for its high salinity.

8. Consider the following rivers: (UPSC CSE Pre 2021)

1. Brahmani
2. Nagavali
3. Subarnarekha
4. Vamsadhara

Which of the above rivers originate from the Eastern Ghats?
 (a) 1 and 2
 (b) 2 and 4
 (c) 3 and 4
 (d) 1 and 3

Solution: (b)
 Exp) Option (b) is the correct answer.

• Statement 1 is incorrect: The Brahmani River originates in Jharkhand, not the Eastern Ghats.
• Statement 2 is correct: The Nagavali River originates in the Eastern Ghats of Odisha.
• Statement 3 is incorrect: The Subarnarekha River originates in Jharkhand, not the Eastern Ghats.
• Statement 4 is correct: The Vamsadhara River originates in the Eastern Ghats and flows into the Bay of Bengal.

9. The black cotton soil of India has been formed due to the weathering of? [UPSC CSE Prelims 2021]

(a) Brown forest soil
(b) Fissure volcanic rock
(c) Granite and schist
(d) Shale and limestone

Solution (2021): (b)
Explanation: Black soil, also known as Regur soil, is formed due to the weathering of fissure volcanic rock. The primary factor contributing to its formation is the climatic condition combined with the basaltic parent rock. These soils are rich in clay and retain moisture for a long period, making them ideal for cotton cultivation. Black soil is predominantly found in Maharashtra, Madhya Pradesh, Gujarat, Karnataka, and Andhra Pradesh, mainly over the Deccan lava plateau.

10. Siachen Glacier is situated to the: [UPSC CSE Prelims 2020]

(a) East of Aksai Chin
(b) East of Leh
(c) North of Gilgit
(d) North of Nubra Valley

Solution (2020): (d)
Explanation: The Siachen Glacier, one of the world's longest glaciers outside the polar regions, is located to the north of Nubra Valley in the eastern Karakoram range. Spanning about 76 km in length, it holds immense strategic importance as it lies near the Line of Control (LoC) between India and Pakistan. The glacier is a contentious region between the two countries and has been a site of military presence for decades.

11. With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? [UPSC CSE Prelims 2020]

• OMT is measured up to a depth of the 26°C isotherm, which is 129 meters in the southwestern Indian Ocean during January–March.
• OMT collected during January–March can help assess whether monsoon rainfall will be more or less than the long-term mean.

Select the correct answer:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Solution (2020): (b)
Explanation:

• Statement 1 is incorrect as the depth of the 26°C isotherm varies between 50–100 meters in the Indian Ocean, depending on seasonal and geographical factors.
• Statement 2 is correct. OMT is a crucial parameter in climate studies and is particularly useful in forecasting monsoon rainfall. Higher ocean temperatures influence atmospheric circulation, which in turn affects monsoon precipitation patterns.

12. Consider the following pairs of famous places and their associated rivers: [UPSC CSE Prelims 2019]

• Pandharpur – Chandrabhaga
• Tiruchirappalli – Cauvery
• Hampi – Malaprabha

Which of the pairs given above are correctly matched?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Solution (2019): (a)
Explanation:

• Pandharpur is situated on the banks of the Chandrabhaga (Bhima) River in Maharashtra.
• Tiruchirappalli (Trichy) is located on the banks of the Cauvery River in Tamil Nadu.
• Hampi, however, is located on the banks of the Tungabhadra River, not the Malaprabha River, making the third pair incorrect.

13. What is common to the places known as Aliyar, Isapur, and Kangsabati? [UPSC CSE Prelims 2019]

(a) Recently discovered uranium deposits
(b) Tropical rainforests
(c) Underground cave systems
(d) Water reservoirs

Solution (2019): (d)
Explanation: Aliyar (Tamil Nadu), Isapur (Maharashtra), and Kangsabati (West Bengal) are all sites of major water reservoirs used for irrigation and water storage purposes.

14. Consider the following pairs of glaciers and their associated rivers: [UPSC CSE Prelims 2019]

• Bandarpunch – Yamuna
• Bara Shigri – Chenab
• Milam – Mandakini
• Siachen – Nubra
• Zemu – Manas

Which of the pairs given above are correctly matched?
(a) 1, 2, and 4 only
(b) 1, 3, and 4 only
(c) 2 and 5 only
(d) 3 and 5 only

Solution (2019): (a)
Explanation:

• Bandarpunch feeds the Yamuna River.
• Bara Shigri Glacier is a tributary of the Chenab River.
• Milam Glacier, however, feeds the Gori Ganga River, not the Mandakini.
• Siachen Glacier is the source of the Nubra River.
• Zemu Glacier feeds the Teesta River, not the Manas.

15. Which one of the following is an artificial lake? [UPSC CSE Prelims 2018]

(a) Kodaikanal (Tamil Nadu)
(b) Kolleru (Andhra Pradesh)
(c) Nainital (Uttarakhand)
(d) Renuka (Himachal Pradesh)

Solution (2018): (a)
Explanation: Kodaikanal Lake is a man-made lake constructed in 1863. The other lakes listed are natural water bodies.

16. Consider the following statements regarding Barren Island Volcano: [UPSC CSE Prelims 2018]

• It is an active volcano in Indian territory.
• It lies about 140 km east of Great Nicobar.
• The last recorded eruption was in 1991, and it has remained inactive since then.

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

Solution (2018): (a)
Explanation:

• Statement 1 is correct. Barren Island is the only active volcano in India, located in the Andaman and Nicobar Islands.
• Statement 2 is incorrect as Barren Island is about 140 km northeast of Port Blair, not Great Nicobar.
• Statement 3 is incorrect because the volcano has erupted multiple times after 1991, including in 2016 and 2017.

17. Among the following cities, which one lies on a longitude closest to that of Delhi? [UPSC CSE Prelims 2018]

(a) Bengaluru
(b) Hyderabad
(c) Nagpur
(d) Pune

Solution (2018): (a)
Explanation: Delhi is at 77.1025°E longitude. Among the options, Bengaluru (77.5946°E) has a longitude closest to Delhi.

18. At one of the places in India, seawater recedes from the shoreline a few kilometers and comes back twice a day. Where is this phenomenon observed? [UPSC CSE Prelims 2017]

(a) Bhavnagar
(b) Bheemunipatnam
(c) Chandipur
(d) Nagapattinam

Solution (2017): (c)
Explanation: This tidal phenomenon occurs at Chandipur Beach, Odisha, where seawater recedes up to 5 km during low tide and returns during high tide, creating a unique natural event.

19. Consider the following statements:

1. In India, the Himalayas are spread over five states only.
2. The Western Ghats are spread over five states only.
3. Pulicat Lake is spread over two states only.

Correct Answer: (b) 3 only

Explanation:

• Statement 1 – Incorrect:
  
  
  • The Himalayas are not confined to just five states; they extend across Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, Assam, West Bengal, and Arunachal Pradesh, making a total of seven
  • These states include major portions of the Greater Himalayas, Lesser Himalayas, and the Outer Himalayas (Shivaliks).
  • The claim that the Himalayas are present in only five states is incorrect.
• Statement 2 – Incorrect:
  
  
  • The Western Ghats, also known as the Sahyadri Hills, extend over six states: Gujarat, Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu.
  • The statement that the Western Ghats are present in only five states is incorrect, as Gujarat is also included.
• Statement 3 – Correct:
  
  
  • Pulicat Lake is the second-largest brackish water lake in India, after Chilika Lake.
  • It is located on the border of Andhra Pradesh and Tamil Nadu, making the statement correct.
  • The lake is famous for being a habitat of flamingos and other migratory birds.

20. What is the minimum number of states one must pass through when traveling from Kohima (Nagaland) to Kottayam (Kerala)?

(a) 6

(b) 7

(c) 8

(d) 9

Correct Answer: (b) 7

Explanation:

The shortest possible route would include the following states:

1. Nagaland (Kohima - Starting Point)
2. Assam
3. West Bengal
4. Odisha
5. Andhra Pradesh
6. Tamil Nadu / Karnataka
7. Kerala (Kottayam - Destination)

Thus, at least seven states need to be crossed while traveling from Kohima to Kottayam using the shortest route.

21. With reference to River Teesta, consider the following statements:

1. The source of River Teesta is the same as Brahmaputra, but it flows through Sikkim.
2. River Rangeet originates in Sikkim and is a tributary of Teesta.
3. River Teesta flows into the Bay of Bengal on the India-Bangladesh border.

Correct Answer: (b) 2 only

Explanation:

• Statement 1 – Incorrect:
  
  
  • The Teesta River originates from the Pahunri (Tso Lhamo) Glacier in North Sikkim.
  • The Brahmaputra River originates from the Chemayungdung Glacier in Tibet and is known as the Yarlung Tsangpo before entering India.
  • Since their origins are different, this statement is incorrect.
• Statement 2 – Correct:
  
  
  • Rangeet River, a major tributary of the Teesta, originates in West Sikkim.
  • It meets the Teesta at Teesta Bazaar in West Bengal, contributing significantly to its flow.
• Statement 3 – Incorrect:
  
  
  • The Teesta does not directly empty into the Bay of Bengal.
  • Instead, it enters Bangladesh and merges with the Jamuna River (the main distributary of the Brahmaputra) before eventually reaching the Bay of Bengal.

22. Indian Ocean Dipole (IOD) and its influence on the Indian Monsoon:

1. IOD is characterized by a temperature difference between the tropical Western Indian Ocean and the Eastern Pacific Ocean.
2. IOD can influence the impact of El Niño on the monsoon.

Correct Answer: (b) 2 only

Explanation:

• Statement 1 – Incorrect:
  
  
  • The Indian Ocean Dipole (IOD) refers to a climatic phenomenon where sea surface temperatures vary between the western and eastern Indian Ocean, not the Eastern Pacific Ocean.
  • A positive IOD occurs when waters in the western Indian Ocean (near Africa) are warmer than in the eastern Indian Ocean (near Indonesia and Australia).
  • A negative IOD is the reverse.
• Statement 2 – Correct:
  
  
  • IOD can significantly modify the impact of El Niño on the Indian monsoon.
  • A positive IOD can reduce the adverse effects of El Niño by strengthening monsoon rainfall over India.
  • Conversely, a negative IOD can worsen the effects of El Niño, leading to reduced monsoon rainfall.

23. Shale Gas Reserves in India

Consider the following basins:

1. Cambay Basin
2. Cauvery Basin
3. Krishna-Godavari Basin

Correct Answer: (d) 1, 2, and 3

Explanation:

Shale gas is an unconventional natural gas trapped within fine-grained sedimentary rocks.

• Cambay Basin (Gujarat): One of the oldest known hydrocarbon basins in India.
• Cauvery Basin (Tamil Nadu): Has significant reserves of shale gas along with conventional hydrocarbons.
• Krishna-Godavari Basin (Andhra Pradesh & Telangana): A key region for both offshore and onshore gas exploration.

All three basins are identified as having shale gas potential, making option (d) the correct answer.

24. The first state in India to have an artificial inland port project is:

(a) Andhra Pradesh

(b) Chhattisgarh

(c) Karnataka

(d) Rajasthan

Correct Answer: (d) Rajasthan

Explanation:

• Rajasthan is developing an artificial inland port in Jalore.
• This port will be connected to the Arabian Sea via the Kutch region of Gujarat, making it a first-of-its-kind project in India.
• The project aims to boost trade and transportation in the landlocked desert region.

25. Recently, India completed the linking of which two rivers?

a) Cauvery–Tungabhadra

(b) Godavari–Krishna

(c) Mahanadi–Son

(d) Narmada–Tapti

Correct Answer: (b) Godavari and Krishna

Explanation:

• The Pattiseema Lift Irrigation Project was implemented in Andhra Pradesh to connect the Godavari River with the Krishna River.
• The objective is to divert surplus water from Godavari to Krishna to tackle water scarcity in the Krishna delta region.

26. Tributaries of the Brahmaputra River:

1. Dibang
2. Kameng
3. Lohit

Correct Answer: (d) 1, 2, and 3

Explanation:

All three rivers are major tributaries of the Brahmaputra River:

• Dibang River: Originates in Arunachal Pradesh and merges with the Brahmaputra.
• Kameng River: Rises in Arunachal Pradesh near the Indo-Tibet border and joins Brahmaputra near Tezpur, Assam.
• Lohit River: Originates in eastern Arunachal Pradesh and joins Brahmaputra near Dibrugarh.

Since all three rivers are Brahmaputra’s tributaries, option (d) is correct.

27. In India, in which one of the following types of forests is teak a dominant tree species?
[UPSC CSE Pre. 2015]
(a) Tropical moist deciduous forest
(b) Tropical rain forest
(c) Tropical thorn scrub forest
(d) Temperate forest with grasslands

Solution: (a)

Teak is the most dominant species of Tropical Moist Deciduous Forests. These forests are also called monsoon forests and are widespread across India. They thrive in areas receiving rainfall between 200 cm and 70 cm. The trees in these forests shed their leaves for about six to eight weeks during dry summer, a characteristic feature of deciduous vegetation.

These forests are further divided into moist deciduous and dry deciduous based on rainfall availability. The moist deciduous forests are found in regions with 200–100 cm rainfall, mainly in the northeastern states, the foothills of the Himalayas, Jharkhand, West Odisha, Chhattisgarh, and the eastern slopes of the Western Ghats.

Apart from teak, these forests also contain bamboo, sal, shisham, sandalwood, khair, kusum, arjun, and mulberry, which are commercially significant species.

28. Consider the following rivers:

1. Vamsadhara
2. Indravati
3. Pranahita
4. Pennar

Which of the above are tributaries of the Godavari River?
[UPSC CSE Pre. 2015]
(a) 1, 2, and 3 only
(b) 2, 3, and 4 only
(c) 1, 2, and 4 only
(d) 2 and 3 only

Solution: (d)

Vamsadhara (1) and Pennar (4) are not tributaries of the Godavari, so the correct answer is (d) 2 and 3 only.

• Vamsadhara River originates in the Kalahandi district of Odisha and flows through Andhra Pradesh before joining the Bay of Bengal. It is a source of dispute between Andhra Pradesh and Odisha.
• Pennar River originates in the Chenna Kasava hill of the Nandidurg range in Karnataka and drains into the Bay of Bengal, making it unrelated to the Godavari system.
• Indravati River and Pranahita River are major tributaries of the Godavari. Pranahita is actually the largest tributary.
• Other left bank tributaries of Godavari include Banganga, Kadva, Shivana, Purna, Kadam, Pranahita, Indravati, Taliperu, Sabari, and Dharna, while right bank tributaries include Nasardi, Pravara, Sindphana, Manjira, Manair, and Kinnerasani.

29. Consider the following States:

1. Arunachal Pradesh
2. Himachal Pradesh
3. Mizoram

In which of the above States do Tropical Wet Evergreen Forests occur?
[UPSC CSE Pre. 2015]
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Solution: (c)

The correct answer is (c) 1 and 3 only because Himachal Pradesh does not have tropical wet evergreen forests.

Tropical Wet Evergreen Forests are found in areas receiving over 200 cm of rainfall with temperatures ranging between 15°C and 30°C. These forests exist at elevations from sea level up to 1000–1200 m and are found in:

• Northeastern states, including Arunachal Pradesh and Mizoram
• Andaman and Nicobar Islands
• Western Ghats in Kerala, Karnataka, and Maharashtra

However, Himachal Pradesh predominantly has temperate and alpine forests such as dry alpine, moist alpine scrub, temperate broadleaf, and subtropical pine forests, making it unsuitable for tropical wet evergreen forests.

30. Which one of the following pairs of States of India indicates the easternmost and westernmost States?
[UPSC CSE Pre. 2015]
(a) Assam and Rajasthan
(b) Arunachal Pradesh and Rajasthan
(c) Assam and Gujarat
(d) Arunachal Pradesh and Gujarat

Solution: (d)

The correct answer is (d) Arunachal Pradesh and Gujarat.

• Easternmost point: Kibithu in Arunachal Pradesh
• Westernmost point: Ghuar Mota in Gujarat (Kutch region, near Sir Creek)

Although Assam is located in the eastern part of India, it is not the easternmost state. Similarly, Rajasthan is located in the western part but does not extend as far west as Gujarat.

31. Consider the following pairs:

Place of Pilgrimage	Location
1. Srisailam	Nallamala Hills
2. Omkareshwar	Satmala Hills
3. Pushkar	Mahadeo Hills

Which of the above pairs is/are correctly matched?
[UPSC CSE Pre. 2015]
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3

Solution: (a)

Only Pair 1 (Srisailam – Nallamala Hills) is correct.

• Srisailam Temple, dedicated to Lord Shiva, is located on the Nallamala Hills in Andhra Pradesh, within the Nagarjunasagar-Srisailam Tiger Reserve.
• Omkareshwar Temple is located on Mandhata Island in Madhya Pradesh and is not associated with the Satmala Hills (which are in Maharashtra).
• Pushkar, known for its Brahma Temple, is situated in the Aravalli Hills of Rajasthan, not in the Mahadeo Hills (which are in Madhya Pradesh). 

32. In a particular region in India, the local people train the roots of living trees into robust bridges across the streams. As time passes, these bridges become stronger. These unique 'living root bridges' are found in:

[UPSC CSE Pre. 2015]
 (a) Meghalaya
 (b) Himachal Pradesh
 (c) Jharkhand
 (d) Tamil Nadu

Solution: (a)

Explanation:
 The Jing Kieng Jri, or living root bridges, are aerial bridges created by weaving and guiding the roots of the Indian rubber tree (Ficus elastica). These bridges, spanning between 15 and 250 feet, have been used by local communities in Meghalaya for centuries. Besides serving as natural connectors over streams and rivers, they have gained global recognition as unique ecological marvels and tourist attractions.

33. Consider the following pairs:

Hills	Region
1. Cardamom Hills	Coromandel Coast
2. Kaimur Hills	Konkan Coast
3. Mahadeo Hills	Central India
4. Mikir Hills	North-East India

Which of the above pairs are correctly matched?
 [UPSC CSE Pre. 2014]
 (a) 1 and 2
 (b) 2 and 3
 (c) 3 and 4
 (d) 2 and 4

Solution: (c)

Explanation:

• Pair 1 is incorrect – The Cardamom Hills (Yela Mala) are part of the Western Ghats in Kerala, not the Coromandel Coast.
• Pair 2 is incorrect – The Kaimur Hills are an eastern extension of the Vindhya Range, stretching from Madhya Pradesh to Bihar, and are not in the Konkan Coast.
• Pair 3 is correct – The Mahadeo Hills are part of the Satpura Range in Madhya Pradesh, central India.
• Pair 4 is correct – The Mikir Hills (Karbi Plateau) are one of the oldest landforms in Assam, Northeast India, covering an area of 7,000 sq. km, with Dambuchko as its highest peak.

34. Which one of the following pairs of islands is separated from each other by the 'Ten Degree Channel'?

[UPSC CSE Pre. 2014]
 (a) Andaman and Nicobar
 (b) Nicobar and Sumatra
 (c) Maldives and Lakshadweep
 (d) Sumatra and Java

Solution: (a)

Explanation:
 The Ten Degree Channel separates the Little Andaman Island (part of Andaman group) and the Nicobar Islands. The channel is approximately 150 km wide and follows an east-west orientation. It is named after the 10-degree latitude line passing through it.

35. The seasonal reversal of winds is the typical characteristic of:

[UPSC CSE Pre. 2014]
 (a) Equatorial climate
 (b) Mediterranean climate
 (c) Monsoon climate
 (d) All of the above climates

Solution: (c)

Explanation:
 A monsoon climate is characterized by a seasonal reversal of wind patterns. This phenomenon is most strongly observed over the Indian subcontinent, where:

• In winter, high-pressure systems in Central Asia cause cold, dry winds to blow from the northeast towards the ocean.
• In summer, a low-pressure system develops over India and Tibet, drawing moist winds from the southwest, bringing heavy rainfall.

This monsoon system significantly influences the climate, agriculture, and water availability in India and other South Asian countries.

36. If you travel through the Himalayas, you are likely to see which of the following plants naturally growing there?

[UPSC CSE Pre. 2014]

1. Oak
2. Rhododendron
3. Sandalwood

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

Solution: (a)

Explanation:

• Oak and Rhododendron are naturally found in the Himalayan region. The Eastern Himalayan broadleaf forests are rich in oak and rhododendron species, with evergreen forests characterized by these trees. The Western Himalayas also have oak-dominated forests.
• Sandalwood is incorrect, as it is an evergreen tree typically found in the tropical dry deciduous forests of Karnataka, Tamil Nadu, Kerala, and Andhra Pradesh, rather than in the Himalayas.

Thus, only options 1 and 2 are correct.

37. Consider the following rivers:

[UPSC CSE Pre. 2014]

1. Barak
2. Lohit
3. Subansiri

Which of the above flows through Arunachal Pradesh?
 (a) 1 only
 (b) 2 and 3 only
 (c) 1 and 3 only
 (d) 1, 2, and 3

Solution: (b)

Explanation:

• Barak River is incorrect, as it originates in Manipur, flows through Mizoram and Assam, and then enters Bangladesh.
• Lohit River is correct – It originates in Tibet, flows through Arunachal Pradesh, and joins the Brahmaputra in Assam.
• Subansiri River is correct – It is another Brahmaputra tributary, originating in Tibet, entering Arunachal Pradesh, and then flowing into Assam.

Thus, only Lohit and Subansiri (options 2 and 3) are correct.

38. With reference to the 'Changpa' community of India, consider the following statements:

[UPSC CSE Pre. 2014]

1. They live mainly in the State of Uttarakhand.
2. They rear the Pashmina goats that yield fine wool.
3. They are classified as a Scheduled Tribe.

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

Solution: (b)

Explanation:

• Statement 1 is incorrect – The Changpa community is a semi-nomadic Tibetan group primarily found in the Changtang region of Ladakh, Jammu & Kashmir, and not Uttarakhand.
• Statement 2 is correct – They are famous for rearing Pashmina goats, which produce the fine Pashmina wool, used to make luxurious shawls.
• Statement 3 is correct – The Changpa community was officially recognized as a Scheduled Tribe in 1989 in India.

Thus, statements 2 and 3 are correct.

ECONOMIC & HUMAN GEOGRAPHY (INDIA AND THE WORLD) 

1. Consider the following statements:

• • Statement-I: India, despite having uranium deposits, depends on coal for most of its electricity production.
  • Statement-II: Uranium, enriched to the extent of at least 60%, is required for the production of electricity.

Which one of the following is correct in respect of the above statements? (UPSC CSE Pre 2023)
(a) Both Statement-I and Statement-II are correct, and Statement-II is the correct explanation for Statement-I.
 (b) Both Statement-I and Statement-II are correct, and Statement-II is not the correct explanation for Statement-I.
 (c) Statement-I is correct, but Statement-II is incorrect.
 (d) Statement-I is incorrect, but Statement-II is correct.

 Solution: (c)
 Exp) Option (c) is the correct answer.

• • Statement-I is correct: Both conventional (thermal, nuclear, hydro) and renewable (wind, solar, biomass, etc.) sources are used for electricity production in India. However, coal-fired thermal power plants dominate, accounting for about 58% of total electricity production, whereas nuclear energy contributes only around 3.15% (2021-2022 data).
  • Statement-II is incorrect: Uranium enrichment for power generation requires only 3-5% enrichment of the U-235 isotope, not 60%. Highly enriched uranium (above 20%) is used for research reactors, and weapons-grade uranium (90%) is used for nuclear weapons.

2. Consider the following pairs:

Port	Claim
Kamarajar Port	First major port in India registered as a company
Mundra Port	Largest privately owned port in India
Visakhapatnam Port	Largest container port in India

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

 Solution: (b)
 Exp) Option (b) is the correct answer.

• • Pair 1 - Kamarajar Port (Correct): It is India’s first corporatized major port, located in Tamil Nadu. It operates as a public company.
  • Pair 2 - Mundra Port (Correct): It is the largest private port in India, located in Gujarat, operated by Adani Ports and SEZ Limited (APSEZ).
  • Pair 3 - Visakhapatnam Port (Incorrect): The largest container port in India is Jawaharlal Nehru Port Trust (JNPT) in Navi Mumbai, not Visakhapatnam.

4. Ilmenite and rutile, abundantly available in certain coastal tracts of India, are rich sources of which one of the following? (UPSC CSE Pre 2023)
(a) Aluminium
 (b) Copper
 (c) Iron
 (d) Titanium

 Solution: (d)
 Exp) Option (d) is the correct answer.

• • Ilmenite (FeTiO₃) and rutile (TiO₂) are titanium-rich minerals found in coastal sands of India.
  • Titanium is widely used in aerospace, automotive, medical, and construction industries due to its strength, lightweight, and corrosion resistance.

5. About three-fourths of the world’s cobalt, a metal required for the manufacture of batteries for electric motor vehicles, is produced by: (UPSC CSE Pre 2023)
(a) Argentina
 (b) Botswana
 (c) The Democratic Republic of the Congo
 (d) Kazakhstan

 Solution: (c)
 Exp) Option (c) is the correct answer.

• • The Democratic Republic of the Congo (DRC) is the largest producer of cobalt, contributing about 75% of global production.
  • Cobalt is crucial for lithium-ion batteries used in electric vehicles (EVs), smartphones, and laptops.
  • The DRC has an estimated 4 million metric tons of cobalt reserves, making it the largest cobalt reserve in the world.

 

6. With reference to India's projects on connectivity, consider the following statements: (UPSC CSE Pre 2023)

1. East-West Corridor under Golden Quadrilateral Project connects Dibrugarh and Surat.
2. Trilateral Highway connects Moreh in Manipur and Chiang Mai in Thailand via Myanmar.
3. Bangladesh-China-India-Myanmar Economic Corridor connects Varanasi in Uttar Pradesh with Kunming in China.

How many of the above statements are correct?
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (d)
 Exp) Option (d) is the correct answer.

• Statement 1 is incorrect: The East-West Corridor connects Silchar in Assam to Porbandar in Gujarat, not Dibrugarh and Surat. It passes through major cities like Guwahati, Gorakhpur, Lucknow, Kanpur, and Ahmedabad.
• Statement 2 is incorrect: The Trilateral Highway connects Moreh in Manipur with Mae Sot in Thailand, not Chiang Mai.
• Statement 3 is incorrect: The BCIM Economic Corridor aims to connect Kunming in China with Kolkata, not Varanasi.

7. Consider the following statements: (UPSC CSE Pre 2023)

• Statement-I: Switzerland is one of the leading exporters of gold in terms of value.
• Statement-II: Switzerland has the second-largest gold reserves in the world.

Which one of the following is correct?
 (a) Both Statement-I and Statement-II are correct, and Statement-II is the correct explanation for Statement-I.
 (b) Both Statement-I and Statement-II are correct, and Statement-II is not the correct explanation for Statement-I.
 (c) Statement-I is correct, but Statement-II is incorrect.
 (d) Statement-I is incorrect, but Statement-II is correct.

Solution: (c)
 Exp) Option (c) is the correct answer.

• Statement-I is correct: Switzerland is the largest exporter of gold, with exports worth $86.7 billion in 2021. Major destinations include India, China, the US, Germany, and Hong Kong.
• Statement-II is incorrect: Switzerland does not have the second-largest gold reserves; it ranks seventh. The top three are the USA, Germany, and Italy.

8. With reference to coal-based thermal power plants in India, consider the following statements: (UPSC CSE Pre 2023)

1. None of them uses seawater.
2. None of them is set up in a water-stressed district.
3. None of them is privately owned.

How many of the above statements are correct?
 (a) Only one
 (b) Only two
 (c) All three
 (d) None

Solution: (d)
 Exp) Option (d) is the correct answer.

• Statement 1 is incorrect: Several coastal power plants like Mundra Thermal Power Plant use seawater for cooling.
• Statement 2 is incorrect: Around 40% of India’s thermal power plants are in water-stressed areas (World Resources Institute).
• Statement 3 is incorrect: India has 269 thermal power plants, with 138 publicly owned and 131 privately owned.

9. With reference to India, consider the following statements: (UPSC CSE Pre 2022)

1. Monazite is a source of rare earths.
2. Monazite contains thorium.
3. Monazite occurs naturally in the entire Indian coastal sands.
4. In India, only government bodies can process or export monazite.

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

Solution: (b)
 Exp) Option (b) is the correct answer.

• Statements 1 and 2 are correct: Monazite is a source of rare earths and contains thorium.
• Statement 3 is incorrect: Monazite is found in specific coastal areas (Kerala, Tamil Nadu, Odisha) but not the entire coastline.
• Statement 4 is correct: Only government-authorized entities (like Indian Rare Earths Limited) can process or export monazite.

10. Consider the following statements: (UPSC CSE Pre 2022)

1. Gujarat has the largest solar park in India.
2. Kerala has a fully solar-powered international airport.
3. Goa has the largest floating solar photovoltaic project in India.

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

Solution: (b)
 Exp) Option (b) is the correct answer.

• Statement 1 is incorrect: Bhadla Solar Park in Rajasthan (2245 MW) is India’s largest solar park, not Gujarat.
• Statement 2 is correct: Cochin International Airport is the world’s first fully solar-powered airport.
• Statement 3 is incorrect: India’s largest floating solar plant is in Andhra Pradesh (Simhadri thermal station, NTPC), not Goa.

11. Consider the following minerals: (UPSC CSE Pre 2020)

1. Bentonite
2. Chromite
3. Kyanite
4. Sillimanite

Which of the above is/are officially designated as major minerals?
 (a) 1 and 2 only
 (b) 4 only
 (c) 1 and 3 only
 (d) 2, 3, and 4 only

Solution: (d)
 Exp) Option (d) is the correct answer.

• Major minerals include chromite, kyanite, and sillimanite, as per the Mines and Minerals (Development and Regulation) Act, 1957.
• Bentonite is classified as a minor mineral.

12. The crop is subtropical in nature. A hard frost is injurious to it. It requires at least 210 frost-free days and 50 to 100 cm of rainfall for its growth. A light, well-drained soil capable of retaining moisture is ideally suited for the cultivation of the crop. (UPSC CSE Pre 2020)

Which one of the following is that crop?
 (a) Cotton
 (b) Jute
 (c) Sugarcane
 (d) Tea

Solution: (a)
 Exp) Option (a) is the correct answer.

• Cotton is a subtropical crop requiring 210 frost-free days, high temperatures (21°C–30°C), and rainfall of 50–100 cm.
• It grows well in light, well-drained soils like black cotton soil in Maharashtra, Gujarat, and Telangana. 

13. With reference to the management of minor minerals in India, consider the following statements: (2019)

1. Sand is a 'minor mineral' according to the prevailing law in the country.
2. State Governments have the power to grant mining leases of minor minerals, but the powers regarding the formation of rules related to the grant of minor minerals lie with the Central Government.
3. State Governments have the power to frame rules to prevent illegal mining of minor minerals.

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

Solution: (a)
Statement 1 is correct. The Mines and Minerals (Development and Regulation) Act, 1957 (MMDR Act) classifies sand as a minor mineral. Minor minerals include building stones, gravel, ordinary clay, and other materials commonly used in construction.
Statement 2 is incorrect. The administration of minor minerals, including the power to grant leases, is entirely under the jurisdiction of the State Governments. They also have the authority to frame rules related to minor minerals, including their extraction, pricing, and regulation. The Central Government provides broad guidelines, but execution and enforcement are handled at the state level.
Statement 3 is correct. Section 23C of the MMDR Act empowers State Governments to create rules to curb illegal mining, regulate transportation, and manage the storage of minor minerals. This provision helps in preventing unregulated extraction, which can lead to environmental degradation and revenue loss for the state.

14. Consider the following statements: (2018)

1. In India, State Governments do not have the power to auction non-coal mines.
2. Andhra Pradesh and Jharkhand do not have gold mines.
3. Rajasthan has iron ore mines.

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

Solution: (d)
Statement 1 is incorrect. The Mines and Minerals (Development and Regulation) Amendment Act, 2015, empowers State Governments to auction non-coal mines. This amendment was introduced to improve transparency in mineral allocation and ensure efficient resource utilization. The auction process is conducted by states under the supervision of the central government.
Statement 2 is incorrect. Gold ore deposits are present in Andhra Pradesh (Ramgiri Goldfields) and Jharkhand (Singhbhum region). Karnataka, however, remains the largest producer of gold in India, with Kolar and Hutti gold mines.
Statement 3 is correct. Rajasthan has substantial iron ore deposits, particularly hematite and magnetite. Key iron ore reserves are located in the districts of Bhilwara and Udaipur. The state contributes significantly to India's overall iron ore production.

15. In which of the following regions of India are shale gas resources found? (2016)

1. Cambay Basin
2. Cauvery Basin
3. Krishna-Godavari Basin

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

Solution: (d)
Shale gas is an unconventional natural gas resource trapped within shale rock formations. In India, significant shale gas reserves have been identified in multiple sedimentary basins. The Cambay Basin (Gujarat), Cauvery Basin (Tamil Nadu), and Krishna-Godavari Basin (Andhra Pradesh) have been recognized for their potential shale gas deposits. The Oil and Natural Gas Corporation (ONGC) has been actively involved in shale gas exploration in these regions.

16. In which of the following activities are Indian Remote Sensing (IRS) satellites used? (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

Solution: (a)
Indian Remote Sensing (IRS) satellites are primarily used for earth observation and resource management. They play a crucial role in crop productivity assessment, groundwater resource mapping, and mineral exploration. These satellites help in precision agriculture, disaster management, and environmental monitoring. However, telecommunications and traffic studies rely on geostationary satellites, such as those from the GSAT series, rather than IRS satellites.

17. Consider the following pairs: (2014)

Region	Well-known for the production of
1. Kinnaur	Areca nut
2. Mewat	Mango
3. Coromandel	Soybean

Which of the above pairs is/are correctly matched? (a) 1 and 2 only
(b) 3 only
(c) 1, 2 and 3
(d) None

Solution: (d)
All three pairs are incorrectly matched.

• Kinnaur, located in Himachal Pradesh, is famous for its high-quality apples and dry fruits, not areca nuts.
• Mewat, covering parts of Haryana and Rajasthan, does not have a significant mango-growing industry.
• The Coromandel region is not known for soybean cultivation; major soybean-producing states are Madhya Pradesh and Maharashtra.

18. Consider the following towns of India: (2014)

1. Bhadrachalam
2. Chanderi
3. Kancheepuram
4. Karnal

Which of the above are famous for the production of traditional sarees/fabric? (a) 1 and 2 only
(b) 2 and 3 only
(c) 1, 2 and 3 only
(d) 1, 3 and 4 only

Solution: (b)
Chanderi (Madhya Pradesh) and Kancheepuram (Tamil Nadu) are renowned for their traditional handwoven sarees. Chanderi sarees are known for their fine silk and intricate patterns, while Kancheepuram sarees are famous for their rich silk and zari work. Bhadrachalam is a religious site, and Karnal is more known for its agricultural significance rather than textile production.

MAPPING

1. The longest border between any two countries in the world is between: [UPSC CSE Pre 2024]

(a) Canada and the United States of America
 (b) Chile and Argentina
 (c) China and India
 (d) Kazakhstan and Russian Federation

Answer: (a) Canada and the United States of America

Explanation:
 The border between Canada and the USA is the longest international border in the world, stretching approximately 8,891 kilometers (5,525 miles). This extensive boundary includes both land and water segments and is renowned for its peaceful nature. The other options have shorter borders:

• Chile and Argentina share a border of about 5,300 kilometers (3,300 miles).
• China and India have a border of approximately 3,488 kilometers (2,167 miles).
• Kazakhstan and the Russian Federation share a border of around 7,644 kilometers (4,750 miles).

2. Consider the following countries: [UPSC CSE Pre 2024]

1. Italy
2. Japan
3. Nigeria
4. South Korea
5. South Africa

Which of the above are members of the G20?

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

Answer: (b) 1, 2 and 5

Explanation:
 The G20, or Group of Twenty, is an international forum comprising 19 countries and the European Union, representing major economies worldwide. Among the listed countries:

• Italy is a founding member of the G20.
• Japan is also a founding member of the G20.
• South Africa joined the G20 in 1999.
• Nigeria and South Korea are not members of the G20.

3. Consider the following pairs: [UPSC CSE Pre 2024]

Country	Important reason for being in the news recently
1. Chad	Setting up a permanent military base by China
2. Guinea	Suspension of its Constitution and Government by military
3. Lebanon	Severe and prolonged economic depression
4. Tunisia	Suspension of Parliament by the President

How many pairs given above are correctly matched?

(a) Only one pair
 (b) Only two pairs
 (c) Only three pairs
 (d) All four pairs

Answer: (c) Only three pairs

Explanation:

• Pair 1 (Chad): There is no significant evidence of China setting up a permanent military base in Chad.
• Pair 2 (Guinea): In 2021, Guinea experienced a military coup that led to the suspension of its Constitution and Government.
• Pair 3 (Lebanon): Lebanon has been undergoing a severe and prolonged economic depression characterized by hyperinflation and political instability.
• Pair 4 (Tunisia): In 2021, Tunisia's President suspended Parliament, citing national emergencies.

4. Which one of the following countries does not have a border with the Mediterranean Sea? [UPSC CSE Pre 2024]

(a) Jordan
 (b) Lebanon
 (c) Syria
 (d) Tunisia

Answer: (a) Jordan

Explanation:
 The Mediterranean Sea is bordered by several countries:

• Lebanon, Syria, and Tunisia all have coastlines along the Mediterranean Sea.
• Jordan, however, does not have a Mediterranean coastline; it has a small shoreline along the Red Sea (Gulf of Aqaba).

5. Which one of the following is a part of the Congo Basin?

[UPSC CSE Pre 2023]

(a) Cameroon
(b) Nigeria
(c) South Sudan
(d) Uganda

Solution: (a) Cameroon

Explanation:
The Congo Basin is a vast geographical region in Central Africa known for the Congo Rainforest, which is the second-largest rainforest in the world after the Amazon. It spans across six countries:

• Cameroon
• Central African Republic
• Democratic Republic of the Congo
• Republic of the Congo
• Equatorial Guinea
• Gabon
• Nigeria (b) is in West Africa and is not part of the Congo Basin.
• South Sudan (c) is in East-Central Africa and does not fall within the Congo Basin.
• Uganda (d), although geographically close to the basin, is not part of it.

6. Consider the following pairs:

Area of Conflict	Country Mentioned
1. Donbas	Syria
2. Kachin	Ethiopia
3. Tigray	North Yemen

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: (d) None

Explanation:

• Pair 1 (Incorrect): Donbas is a region in Ukraine, not Syria. It includes Donetsk and Luhansk, which are conflict zones due to separatist movements supported by Russia.
• Pair 2 (Incorrect): Kachin is a state in Myanmar (Burma), not Ethiopia. It has been a site of conflict between the Kachin Independence Army and the Myanmar military.
• Pair 3 (Incorrect): Tigray is a region in Ethiopia, not North Yemen. It has been a focal point of the Tigray War between the Tigray People's Liberation Front (TPLF) and the Ethiopian government.

Thus, none of the pairs are correctly matched.

7. How many of the following countries share a land border with Ukraine?

[UPSC CSE Pre 2023]

Countries Given:

1. Bulgaria
2. Czech Republic
3. Hungary
4. Latvia
5. Lithuania
6. Romania

(a) Only two
(b) Only three
(c) Only four
(d) Only five

Solution: (a) Only two

Explanation: Ukraine shares land borders with:

• Belarus (North)
• Russia (East)
• Poland (West)
• Slovakia (West)
• Hungary (West)
• Romania (Southwest)
• Moldova (Southwest)

From the given list, only Hungary and Romania share land borders with Ukraine.

• Bulgaria, Czech Republic, Latvia, and Lithuania do not share a border with Ukraine.

Thus, the correct answer is only two countries.

8. Which of the following countries have borders with Afghanistan?

[UPSC CSE Pre 2022]

1. Azerbaijan
2. Kyrgyzstan
3. Tajikistan
4. Turkmenistan
5. Uzbekistan

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

Solution: (c) 3, 4, and 5 only

Explanation: Afghanistan shares borders with six countries:

1. Pakistan (Longest border)
2. Iran
3. Turkmenistan
4. Uzbekistan
5. Tajikistan
6. China

• Azerbaijan (1) and Kyrgyzstan (2) do not share borders with Afghanistan.
• Tajikistan (3), Turkmenistan (4), and Uzbekistan (5) all have direct borders with Afghanistan.

Thus, the correct answer is 3, 4, and 5 only.

9. Consider the following pairs:

[UPSC CSE Pre 2022]

Region Often Mentioned	Country
1. Anatolia	Turkey
2. Amhara	Ethiopia
3. Cabo Delgado	Spain
4. Catalonia	Italy

How many of the above pairs are correctly matched?

(a) Only one pair
(b) Only two pairs
(c) Only three pairs
(d) All four pairs

Solution: (b) Only two pairs

Explanation:

• Pair 1 (Correct): Anatolia is a large peninsula in Turkey, forming its Asian part.
• Pair 2 (Correct): Amhara is a region in Ethiopia.
• Pair 3 (Incorrect): Cabo Delgado is a province in Mozambique, not Spain.
• Pair 4 (Incorrect): Catalonia is a region in Spain, not Italy.

Thus, only two pairs are correctly matched.

10. Consider the following pairs: (UPSC CSE Pre. 2020)

River	Flows into
1. Mekong	Andaman Sea
2. Thames	Irish Sea
3. Volga	Caspian Sea
4. Zambezi	Indian Ocean

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

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

Solution: (c)
Explanation:

• Option 1 is incorrect. The Mekong River originates in Tibet, flows through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam before draining into the South China Sea, not the Andaman Sea.
• Option 2 is incorrect. The Thames River, the longest river in England, drains into the North Sea, not the Irish Sea.
• Option 3 is correct. The Volga River, the longest river in Europe, originates in the Valdai Hills northwest of Moscow and discharges into the Caspian Sea.
• Option 4 is correct. The Zambezi River, a major river in Africa, originates in Zambia and flows through Angola, Namibia, Botswana, Zimbabwe, and Mozambique before draining into the Indian Ocean.

11. Consider the following pairs: (UPSC CSE Pre. 2019)

Sea	Bordering country
1. Adriatic Sea	Albania
2. Black Sea	Croatia
3. Caspian Sea	Kazakhstan
4. Mediterranean Sea	Morocco
5. Red Sea	Syria

Which of the pairs given above are correctly matched?

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

Solution: (b)
Explanation:

• Pair 1 is correct. The Adriatic Sea borders Albania.
• Pair 2 is incorrect. The Black Sea borders Russia, Turkey, Georgia, Romania, Ukraine, and Bulgaria, not Croatia. The Adriatic Sea borders Croatia.
• Pair 3 is correct. The Caspian Sea is bordered by Russia, Iran, Azerbaijan, Kazakhstan, and Turkmenistan.
• Pair 4 is correct. Morocco borders the Mediterranean Sea near the Strait of Gibraltar.
• Pair 5 is incorrect. The Red Sea borders Egypt, Sudan, Yemen, Saudi Arabia, Eritrea, and Djibouti. Syria is bordered by the Mediterranean Sea.

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

Regions sometimes mentioned in news	Country
1. Catalonia	Spain
2. Crimea	Hungary
3. Mindanao	Philippines
4. Oromia	Nigeria

Which of the pairs given above are correctly matched?

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

Solution: (c)
Explanation:

• Pair 1 is correct. Catalonia is an autonomous region in Spain that has sought independence.
• Pair 2 is incorrect. Crimea was part of Ukraine until 2014 when it was annexed by Russia.
• Pair 3 is correct. Mindanao is an island in the Philippines that has experienced conflicts over autonomy.
• Pair 4 is incorrect. Oromia is a region in Ethiopia, not Nigeria, with movements advocating for autonomy.

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

Towns sometimes mentioned in news	Country
1. Aleppo	Arabia
2. Kirkuk	Yemen
3. Mosul	Palestine
4. Mazar-i-Sharif	Afghanistan

Which of the pairs given above are correctly matched?

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

Solution: (b)
Explanation:

• Pair 1 is correctly matched. Aleppo is a city in northern Syria, not Arabia, but it was a significant conflict zone.
• Pairs 2 and 3 are incorrectly matched. Kirkuk and Mosul are cities in Iraq, not Yemen or Palestine.
• Pair 4 is correct. Mazar-i-Sharif is a city in Afghanistan.

14. Which of the following is geographically closest to Great Nicobar? (UPSC CSE Pre. 2017)

(a) Sumatra
(b) Borneo
(c) Java
(d) Sri Lanka

Solution: (a)
Explanation:

• Sumatra is the closest to Great Nicobar, at a distance of approximately 1,192 km.
• Java is farther at around 1,817 km.
• Borneo is even farther at approximately 2,398 km.
• Sri Lanka is around 1,437 km away. 

15.  Mediterranean Sea is a border of which of the following countries?

[UPSC CSE Pre. 2017]

Options:

1. Jordan
2. Iraq
3. Lebanon
4. Syria

Correct Answer: (c) 3 and 4 only

Explanation:

The Mediterranean Sea is bordered by multiple countries in Europe, Africa, and the Middle East. The relevant countries in the Middle East with a Mediterranean coastline include Turkey, Syria, Lebanon, Israel, and Palestine (Gaza Strip).

• Jordan does not have a Mediterranean coastline. It is bordered by Syria, Iraq, Saudi Arabia, and Israel, with a small opening to the Red Sea at the Gulf of Aqaba.
• Iraq is also landlocked concerning the Mediterranean Sea. It has a small coastline, but only on the Persian Gulf in the south.
• Lebanon and Syria both have a Mediterranean coastline, making them the correct answers.

Thus, the countries bordering the Mediterranean Sea from the given list are Lebanon and Syria (Option C: 3 and 4 only).

16. If you travel by road from Kohima to Kottayam, what is the minimum number of states within India through which you can travel, including the origin and the destination?

[UPSC CSE Pre. 2017]

Options:

(a) 6
 (b) 7
 (c) 8
 (d) 9

Correct Answer: (b) 7

Explanation:

To determine the minimum number of states required to travel by road from Kohima (Nagaland) to Kottayam (Kerala), we need to find the shortest possible route:

1. Nagaland (Origin)
2. Assam
3. West Bengal
4. Odisha
5. Andhra Pradesh
6. Tamil Nadu or Karnataka
7. Kerala (Destination)

Thus, the minimum number of states required is 7 (Option B).

17. Which one of the following countries of South-West Asia does not open out to the Mediterranean Sea?

[UPSC CSE Pre. 2015]

Options:

(a) Syria
 (b) Jordan
 (c) Lebanon
 (d) Israel

Correct Answer: (b) Jordan

Explanation:

The Mediterranean Sea borders Syria, Lebanon, Israel, and many other European and African nations.

• Syria has a coastline on the Mediterranean.
• Lebanon has a coastline on the Mediterranean.
• Israel has a coastline on the Mediterranean.
• Jordan does NOT have a Mediterranean coastline. It is landlocked except for a small 26 km coastline on the Red Sea (Aqaba).

Thus, the country that does not open out to the Mediterranean Sea is Jordan (Option B).

18. Turkey is located between:

[UPSC CSE Pre. 2014]

Options:

(a) Black Sea and Caspian Sea
 (b) Black Sea and Mediterranean Sea
 (c) Gulf of Suez and Mediterranean Sea
 (d) Gulf of Aqaba and Dead Sea

Correct Answer: (b) Black Sea and Mediterranean Sea

Explanation:

Turkey is a transcontinental country located at the junction of Europe and Asia.

• To the north: It is bordered by the Black Sea.
• To the south: It is bordered by the Mediterranean Sea.

Other options are incorrect:

• The Caspian Sea does not touch Turkey.
• The Gulf of Suez and Gulf of Aqaba are near Egypt and Jordan, not Turkey.
• The Dead Sea is in Jordan and Israel.

Thus, Turkey is located between the Black Sea and the Mediterranean Sea (Option B).

19. What is the correct sequence of occurrence of the following cities in South-East Asia as one proceeds from south to north?

[UPSC CSE Pre. 2014]

Cities:

1. Bangkok
2. Hanoi
3. Jakarta
4. Singapore

Options:

(a) 4-2-1-3
 (b) 3-2-4-1
 (c) 3-4-1-2
 (d) 4-3-2-1

Correct Answer: (c) 3-4-1-2

Explanation:

To arrange the cities from south to north, we check their latitudes:

1. Jakarta (Indonesia) – Located farthest south
2. Singapore – North of Jakarta
3. Bangkok (Thailand) – North of Singapore
4. Hanoi (Vietnam) – Farthest north

Thus, the correct sequence is Jakarta → Singapore → Bangkok → Hanoi (Option C).

20. Consider the following pairs:

[UPSC CSE Pre. 2014]

National Highways and Cities Connected:

National Highway	Cities Connected
NH4	Chennai and Hyderabad
NH6	Mumbai and Kolkata
NH15	Ahmedabad and Jodhpur

Options:

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

Correct Answer: (d) None of the above

Explanation:

Due to the renumbering of Indian National Highways in 2010, the original NH numbers have changed:

1. NH4: The old NH4 was part of the Golden Quadrilateral connecting Mumbai to Chennai via Pune and Bengaluru. It does not connect Chennai and Hyderabad. The new NH4 is now the Andaman Trunk Road (ATR) in the Andaman and Nicobar Islands.
2. NH6: The old NH6 connected Surat to Kolkata, but it did not directly connect Mumbai and Kolkata. The new NH6 is now in Meghalaya (Jorabat to Zokhawthar).
3. NH15: The old NH15 ran through Punjab and Rajasthan, but not Ahmedabad and Jodhpur. The new NH15 runs through Assam and Arunachal Pradesh.

Since none of the options correctly match the current NH system, the correct answer is (d) None of the above.