Relative humidity may change due to: (a) a change in temperature-cold air has a low water-vapor capacity, while warm air has a high capacity, or (b) a change in the amount of water vapor in the air.

Both (A) and (B)

Explanation:

Relative humidity usually refers to the quantity of water vapor that is present in the air in order to get saturated at the same given temperature. It is expressed in terms of percentage (%).

This relative humidity can be primarily changed in two different ways, such as-

(A) By changing the air temperature - Temperature is an important factor here, as by increasing or decreasing the air temperature, the relative humidity can be altered.

(B) By changing the amount of water vapor present in the air - The amount of water vapor that air can store gradually increases with the rise in temperature. So the warm air contains more moisture content in comparison to the cold air, thereby having high relative humidity.

Thus, both (A) and (B) are the correct answers.