If the actual amount of water vapour does not change but air cools, what result is possible?

Correct answer: Relative humidity will increase

Direct answer: B, relative humidity will increase. Relative humidity compares the water vapour actually present with the maximum amount the air can hold at that temperature. Cooling lowers the air’s saturation capacity. If the actual amount of vapour stays unchanged while the capacity becomes smaller, the ratio of actual vapour to possible vapour becomes larger. For example, the same amount of water vapour occupies a greater percentage of the available capacity in cooler air. A is wrong because cooling generally makes relative humidity rise, not fall. C is wrong because cooling does not remove all moisture from the air. D is wrong because evaporation depends on several factors, and cooling does not necessarily increase it; it often reduces evaporation. If cooling continues until the dew point is reached, condensation may begin. Memory cue: same vapour plus less holding capacity means higher relative humidity.