Which of the following complexes is an example of the $MA_2BC$ type of stereoisomers?

The number of geometrical isomers for octahedral $[CoCl_4(NH_3)_2]^-$,square planar $[AuBr_2Cl_2]^-$ and $[PtCl_2(en)]$ are

Indicate the types of isomerism exhibited by the following complexes and draw the structures for these isomers:
$(i)$ $K[Cr(H_2O)_2(C_2O_4)_2]$
$(ii)$ $[Co(en)_3]Cl_3$
$(iii)$ $[Co(NH_3)_5(NO_2)](NO_3)_2$
$(iv)$ $[Pt(NH_3)(H_2O)Cl_2]$

$Cis-trans$ isomerism is found in square planar complexes of the molecular formula: ($A$ and $B$ are monodentate ligands):

The magnetic moments of the complexes given below are in the order:
$I. [Ni(CO)_4]$
$II. [Mn(CN)_6]^{4-}$
$III. [Cr(NH_3)_6]^{3+}$
$IV. [CoF_6]^{3-}$

Which of the following does not show optical isomerism?