In which of the following pairs both the complexes show optical isomerism?
A. `Cis-[CrCl_(2)(OX)_(2)]^(2-),"trans"-[CrCl_(2)(OX)_(2)]^(3-)`
B. `[Fe(NH_(3))_(2)(CN)_(4)]^(-)[Fe(en)_(3)]^(3+)`
C. `Cis-[Pt(en)_(2)Cl_(2)]^(2+),[Co(en)_(3)]^(3+)`
D. `Cis-[Co(NH_(3))_(4)(NO_(2))_(2)]^(+),cis(Cr(gly)_(3)]`
