Which one of the following has an optical isomer ? (en = ethylenediamine)

Question

Which one of the following has an optical isomer ?
(en = ethylenediamine)

[Zn (en) (NH₃)₂]²⁺

[Co (en)₃]³⁺

[Co (H₂O)₄ en]³⁺

[Zn (en)₂]²⁺

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