Which of the following statements is true:
$\left(\mathrm{A}\right){\mathrm{Ma}}_3{\mathrm{b}}_3$ type of complex exhibits fac-mer isomerism
$\left(B\right)$ Tetrahedral complexes do not exhibit optical isomerism
$\left(\mathrm{C}\right) [\mathrm{Co}{\left(\mathrm{en}\right)}_3{]}^{3+}$ shows optical isomerism
$\left(\mathrm{D}\right)\left[\mathrm{Pt}{\left(\mathrm{en}\right)}_2{\mathrm{Cl}}_2\right]$ does not exhibit optical isomerism