Which of the following does not show optical isomerism - <br> (en = Ethylenediamine)

Question

( A ) $[Co(en)_3]^{3+}$
( B ) $[Co(NH_3)_3Cl_3]^{\circ}$
( C ) $[Co(en)_2Cl_2]^+$
( D ) $[Co(en)Cl_2(NH_3)_2]^+$