On an increase in absolute humidity and temperature, what is the effect on the relative humidity? 

Humidity is the amount of water present in the air. Relative humidity is defined as the ratio of partial vapor pressure of water in the air represented by $p_{{\mathrm{H}}_2\mathrm{O}}$ to the saturation vapor partial pressure represented by $p^{*}{\mathrm{H}}_2\mathrm{O}$, relative humidity is given by the formula $\varphi =\frac{p_{{\mathrm{H}}_2\mathrm{O}}}{{p^{*}}_{{\mathrm{H}}_2\mathrm{O}}}$. Here $\varphi$ is relative humidity. The vapour pressure that exists when the water content reaches saturation is what we refer to as saturation vapour partial pressure. An equilibrium has been created at saturation level. This indicates that an equal amount of water molecules are condensing back into the liquid water and an equal number are evaporating from the surface of the water.
The total mass of water vapour in a given volume is the definition of absolute humidity. It is not temperature-dependent. Relative humidity and temperature are inversely correlated. Accordingly, relative humidity drops as temperature rises.

Hence, the correct option is (B).