Which of the following does not have optical isomers?

Which of the following compounds does not exhibit optical isomerism? $(en = \text{ethylenediamine})$

Which of the following coordination compounds exhibit both optical and geometrical isomerism?
$a$. $[Co(en)_2Cl_2]Br$
$b$. $[Pt(NH_3)_2Cl_2Br_2]$
$c$. $[Co(en)_3]Cl_3$
$d$. $[Pt(NH_3)_4Cl_2]$
$e$. $[Pt(NH_3)_2Cl_2]$

The correct structures of trans-$[NiBr_{2}(PPh_{3})_{2}]$ and meridional-$[Co(NH_{3})_{3}(NO_{2})_{3}]$,respectively,are

The complex compounds $[Co(NH_3)_5 SO_4] Br$ and $[Co(NH_3)_5 Br] SO_4$ are

If $[Co(NH_3)_x(NO_2)_y]$ shows facial and meridional isomers,identify the values of $x$ and $y$.