The correct statement on the isomerism associated with the following complex ions,$(a) [Ni(H_2O)_5NH_3]^{2+},\\ (b) [Ni(H_2O)_4(NH_3)_2]^{2+} \;and\\ (c) [Ni(H_2O)_3(NH_3)_3]^{2+}\; is :$

Question

$\begin{array}{1 1} \text{(a) and (b) show only geometrical isomerism} \\ \text{ (a) and (b) show geometrical and optical isomerism} \\ \text{(b) and (c) show geometrical and optical isomerism} \\ \text{ (b) and (c) show only geometrical isomerism} \end{array}$