The total number of geometrical isomers for the given complexes are [NiCl4]2− - No geometrical isomer [CoCl2(NH3)4]+- octahedral complex of the type MA4B2. So can exist as cis and trans isomers. Thus 2 geometrical isomers are possible. [ Co(NH3)3(NO2)3 ] - Octahedral complex of the type MA3B3. So can exist as facial and meridional isomer. So, 2 geometrical isomers are possible. [Co(NH3)5Cl]2+ - Octahedral complex of the type MA5B. All positions are equivalent relative to the single unique ligand. So no geometrical isomer is possible. Thus, total 4 geometrical isomers are possible.