The correct option is D It is expressed in the ratio of amount of water vapour present in the air at a given temperature and that of amount of water vapour air can hold at that temperature.
Relative
humidity is expressed as the amount of water vapor in the air as a percentage
of the total amount that could be held at its current temperature. Absolute
humidity is the measure of water vapor in the air, regardless of temperature.
Relative humidity is cited in weather forecasts. It affects how we feel
temperature. That’s why relative humidity is important.