When is the rate of evaporation lower?

Correct answer: When air is more humid

Direct answer: A, when the air is more humid. Evaporation is faster when water vapour can move away from a wet surface. Highly humid air already contains a large amount of vapour, so it has less capacity to receive additional vapour. The difference between the wet surface and surrounding air is smaller, and evaporation slows. B is wrong because higher temperature generally gives water molecules more energy and increases evaporation. C is wrong because strong wind usually removes moist air from the surface and increases evaporation. D is wrong because an open, exposed surface generally allows more contact with air and can support faster evaporation than a covered surface, all else being equal. The rate also depends on temperature, wind, exposed area and dryness of the air, but among these choices high humidity clearly lowers it. Memory cue: humid air is already “fuller” of vapour, so water escapes less readily. Do not confuse high humidity with high evaporation; high humidity commonly suppresses evaporation.