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.

The correct answer is 1 only.

Let us analyze the statements step-by-step to understand why this option is correct:

Analysis of Statement 1:
Water vapour is indeed the gaseous state of water in the atmosphere. The concentration of water vapour is highest near the Earth's surface (especially in the troposphere) and decreases rapidly as the altitude increases. This is because gravity keeps the atmosphere denser closer to the surface, and the temperature drops with altitude in the troposphere, which reduces the air's capacity to hold water vapour. Therefore, Statement 1 is correct.

Analysis of Statement 2:
The capacity of air to hold moisture depends directly on its temperature. Warm air can hold much more water vapour than cold air. The polar regions are extremely cold, which means the air there has a very low capacity to hold moisture, leading to a minimal percentage of water vapour (often less than 0.2%). In contrast, the maximum concentration of water vapour is found in the warm, humid tropical regions near the equator, where it can make up to 4% of the atmosphere. Therefore, Statement 2 is incorrect.

Since only the first statement is correct, the correct code is 1 only.