Which of the following complex has three stereo isomers and exhibits both geometrical and optical isomersism(a,b,c.d=monodentate ligands; aa=symmetrical bidentate ligand)

• A

  $\left[\mathrm{Mabcd}\right]$

• B

  $\left[{\mathrm{Ma}}_4{\mathrm{b}}_2\right]$

• C

  $\left[\mathrm{M}{\left(\mathrm{aa}\right)}_2{\mathrm{b}}_2\right]$

• D

  $\left[{\mathrm{Ma}}_3{\mathrm{b}}_3\right]$