Which has largest number of isomers

Which one of the following has largest number of isomers? (R = alkyl group, en = ethylenediamine)

  1. [Co(en)2Cl2]+
  2. [Co(NH3)5Cl]2+
  3. [Ir(PR3)2H(CO)]2+
  4. [Ru(NH3)4Cl2]+

Answer

[Co(en)2Cl2]+ shows geometrical as well as optical isomerism.

The correct option is A.