Hydrated copper sulphate CuSO4⋅5H2O is blue in colour. The ligand (water) molecules causes splitting of d -orbitals. This facilitated d−d transition and colour. Anhydrous copper sulphate CuSO4 is colourless. In the absence of ligand (water) molecules, splitting of d -orbitals is not possible. Hence, d−d transition is not possible. Hence, option (b) is correct.