People, Development and Environment - People, Development and Environment Section 1
- A
About 97.5 per cent of the total volume of water available on the earth is salty
- B
80 per cent of the water available to us for use comes in bursts as monsoons
- C
About 2.5 per cent of the total water available on the earth is polluted water and cannot be used for human activities
- D
Possibility is that some big glaciers will melt in the coming ten-fifteen years and sea level will rise by 3-4 meters all over the earth
- Option : C
- Explanation :
A. About 97.5 per cent of the total volume of water available on the earth is salty
True — Around 97.5% of Earth’s water is in oceans and seas and is saline, leaving very little as freshwater.B. 80 per cent of the water available to us for use comes in bursts as monsoons
True — A large proportion of usable freshwater in India (and many tropical areas) arrives seasonally during monsoons.C. About 2.5 per cent of the total water available on the earth is polluted water and cannot be used for human activities
Not true — About 2.5% of total water is freshwater, not polluted water. Though freshwater resources can be polluted, the 2.5% refers to freshwater available in glaciers, groundwater, etc.D. Possibility is that some big glaciers will melt in the coming ten-fifteen years and sea level will rise by 3-4 meters all over the earth
Broadly true in terms of glacier melting, but exaggerated on sea level rise; scientists project sea level to rise by a few centimeters to around a meter by the end of the century, not 3–4 meters in just 10–15 years.Answer: C is not true.
17. Different seasons are formed because
- Option : D
- Explanation :
The correct reason for the formation of seasons is that the Earth is tilted on its axis as it revolves around the Sun.
This axial tilt (approximately 23.5°) causes different parts of the Earth to receive varying amounts of sunlight during the year, leading to summer,winter, spring, and autumn in different hemispheres.- Option A: Sun is moving around the earth
Incorrect. This is a geocentric view, which has been scientifically disproven. The Earth orbits the Sun, not the other way around. - Option B: Revolution of the earth around the Sun on its orbit
Partially true, but not complete. Revolution alone doesn’t cause seasons unless the tilt of the axis is also considered. Without tilt, every place would receive the same type of light year-round. - Option C: Rotation of the earth around its axis
Incorrect. Earth's rotation causes day and night, not seasons. - Option D: Because Earth is tilted when it revolves around the Sun
Correct answer. The tilt + revolution together cause changing angles of sunlight, which leads to seasonal changes.
- Option A: Sun is moving around the earth
- Option : A
- Explanation :
Statements 1 and 3 are correct.
Correct Statements:
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Statement 1: Ozone is found mostly in the Stratosphere
True. About 90% of the Earth's ozone resides in the stratosphere, forming the ozone layer, typically between 15 to 35 km above the Earth’s surface. -
Statement 3: Ozone absorbs ultraviolet radiation from the Sun
True. The ozone layer absorbs harmful UV-B and UV-C radiation, protecting life on Earth from its damaging effects (like skin cancer and eye problems).
Incorrect Statements:
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Statement 2: Ozone layer lies 55–75 km above the surface of the earth
Statement 4: Ozone layer has no significance for life on the earth -
Option A (1 and 3)
Both statements are correct — this is the correct answer.
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19. The natural vegetation of Savana consists of:
- Option : A
- Explanation :
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Option A: Tall grass
Correct. Tall grasses dominate the savanna biome, often growing up to 2–3 meters during the wet season. This is the most accurate description of savanna vegetation. -
Option B: Scrub jungle
This refers more to arid or semi-arid regions (like thorn forests), not typical of savannas. -
Option C: Short grass
Found in temperate grasslands (like prairies or steppes), not in tropical savannas. -
Option D: Trees
Trees are sparse in savannas due to the seasonal droughts and fires. While present, they’re not the dominant vegetation.
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20. The much discussed Tehri Dam Project is located in which of the following states?
- Option : D
- Explanation :
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Option A: Madhya Pradesh
Home to dams like Bargi and Indira Sagar, but not Tehri. -
Option B: Rajasthan
Has water projects like Bisalpur Dam, but Tehri is not here. -
Option C: Haryana
No major hill rivers to support a project like Tehri Dam. -
Option D: Uttaranchal (now Uttarakhand)
Correct Answer. Tehri Dam is located here, in the Himalayan region of India.
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