The moisture holding capacity of air increases with increase in what?

Correct answer: Temperature

Correct answer: A, temperature. In general, warmer air has a greater capacity to contain water vapour than colder air. When temperature rises, the saturation amount of water vapour that air can hold increases. This statement concerns capacity, not necessarily the actual amount of vapour already present: air can become warmer without immediately gaining more vapour. A is correct because temperature directly affects the saturation capacity of air. B is wrong because shade may reduce heating but is not the basic atmospheric variable being asked about. C is wrong because darkness itself does not determine how much vapour air can hold. D is wrong because dust may provide surfaces on which condensation occurs, but it does not define the moisture-holding capacity of air. A useful caution is that warm air does not automatically mean high relative humidity; if its actual vapour remains unchanged, relative humidity may fall as temperature rises. Memory cue: warm air can hold more vapour; cooling brings it closer to saturation.