How many water molecules are present in one formula unit of ${\text{CuSO}}_4.5{\text{H}}_2\text{O}$?

1. 5

The correct option is A 5
The water of crystallization is the fixed number of water molecules in one formula unit of a salt. Thus, in case of ${\text{CuSO}}_4.5{\text{H}}_2\text{O}$, there are five water molecules.