Which one of the following has three stereoisomers and shows both optical and geometrical isomerism.

• A

  Square planar $\left[\mathrm{PtBrCl}\left({\mathrm{NH}}_3\right)\left(\mathrm{Py}\right)\right]$

• B

  Tetrahedral $\left[\mathrm{ZnBrCl}\left({\mathrm{NH}}_3\right)\left(\mathrm{Py}\right)\right]$

• C

  Octahedral  ${\left[{\mathrm{CoCl}}_2{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_2\right]}^{-3}$

• D

  Octehedral ${\left[\mathrm{Co}{\left(\mathrm{en}\right)}_3\right]}^{+3}$