Question

¹rate of evaporation of an aqueous solution decrease with increase in humidity

Answer 1

This is because due to humidity there are already many water molecules in the atmosphere which prevents further evaporation of water

Answer 2

Humidity is basically the amount of water vapour in the air. And evaporation is the vaporization of water into water vapour. So when the humidity is high there are already plenty of water molecules in the air so the water which gets vapourized into water vapour takes time to fill the gaps in the atmosphere and thus rate of evaporation is slow. (It's like filling intermolecular space, only here the space isn't between molecules.)

The above answerr is what my teacher told me.

Here's another possible answer

For a liquid to vapourize it needs to the temperature needs to be at a particular temperature so that this surface phenomena can take place. But due to high amount of water vapours in the atmosphere which is nothing but high humidity the temperature needed to vapourize the liquid isn't reached as the water vapour lowers the surface temperature.