Which one of the following statements is correct ?

The number of water of crystallization molecules varies among different metal sulfate salts. Copper sulphate (blue vitriol) typically exists as a pentahydrate, represented by the chemical formula CuSO4·5H2O, meaning it contains five molecules of water of crystallization. In contrast, iron sulphate (green vitriol) and zinc sulphate (white vitriol) both commonly exist in their heptahydrate forms. Iron sulphate is represented as FeSO4·7H2O, and zinc sulphate is represented as ZnSO4·7H2O. Since both iron sulphate and zinc sulphate crystals contain seven molecules of water of crystallization per formula unit, they have the same number of water of crystallization. Copper sulphate differs from these two as it only has five molecules. Therefore, the statement that iron sulphate and zinc sulphate have the same number of water of crystallization is correct.