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 :

1. A. 1 only
2. B. 2 only
3. C. Both 1 and 2
4. D. Neither 1 nor 2

Answer: A

Explanation

Statement 1 is correct: Water vapour is a variable gas in the atmosphere, and its concentration significantly decreases with increasing altitude. Most of the atmospheric water vapour is concentrated in the lower troposphere, close to the Earth’s surface, due to evaporation from water bodies and land. Statement 2 is incorrect: The amount of water vapour in the atmosphere is primarily influenced by temperature and proximity to moisture sources. It is highest in warm, humid tropical regions near the equator and decreases towards the colder, drier polar regions. Therefore, its percentage is minimum, not maximum, at the poles. This question pertains to fundamental concepts of physical geography and atmospheric composition, which are core to the UPSC Geography syllabus.