With reference to "water vapour", which of the following statements is/are correct ?
- 1.It is a gas, the amount of which decreases with altitude.
- 2.Its percentage is maximum at the poles.
Select the answer using the code given below :
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Answer: A. Statement 1 is correct: water vapour comes from evaporation at the surface, so its amount falls with height. Statement 2 is wrong: water vapour is highest in warm, wet tropical air (up to about 4% by volume) and lowest in cold, dry polar air (under 1%). So only 1.
Watch for: Students link ice at the poles with lots of water, but cold air can hold very little water vapour.
Why the other options are wrong
- B. Wrong because water vapour is least, not most, at the poles.
- C. Wrong because Statement 2 is false; cold polar air holds little moisture.
- D. Wrong because Statement 1 is true; water vapour decreases with altitude.
Source to check: NCERT Class 11 Fundamentals of Physical Geography, Chapter 7 'Composition and Structure of Atmosphere' and Chapter 10 'Water in the Atmosphere'
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.