(C) The rate of evaporation will be the highest in vessel $C$.
Explanation:
$1$. Evaporation is a surface phenomenon,meaning it occurs only at the surface of a liquid. Therefore,the rate of evaporation increases with an increase in the surface area of the liquid exposed to the atmosphere.
$2$. Vessel $C$ has the largest surface area compared to vessels $A$ and $B$.
$3$. Additionally,the presence of a moving fan above vessel $C$ increases the wind speed. An increase in wind speed causes the water vapour particles to move away faster,thereby increasing the rate of evaporation.
$4$. Vessel $D$ is covered,which prevents evaporation from occurring effectively.