Indicate the complex ion which shows geometrical isomerism-

1. Cr(H2O)4Cl2+

2. Pt(NH3)3Cl

3. Co(NH3)63+

4. Co(CN)63-

Hint: General formula [M(A)4(B)2] show geometrical isomerism

Cr(H2O)4Cl2+shows geometrical isomerism because it is a MAB, type coordination

compound which contains two set of equivalent ligands, four HO and 2 Cl.

Hence, the possible geometrical isomers are

Hence, correct choice is (a).