Which one of the following complexes shows optical isomerism? (en=ethylendiamine)

$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$ shows two geometrical isomers and both can't show optical isomerism due to presence of plane of symmetry.



$\mathrm{c}\mathrm{i}\mathrm{s}\mathrm{ }\left[\mathrm{C}\mathrm{o}{\left(\mathrm{e}\mathrm{n}\right)}_2\mathrm{C}{\mathrm{l}}_2\right]\mathrm{C}\mathrm{l}$ shows optical isomerism




$\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{s}\mathrm{ }\mathrm{ }\left[\mathrm{Co}{\left(\mathrm{e}\mathrm{n}\right)}_2\mathrm{C}{\mathrm{l}}_2\right]\mathrm{C}\mathrm{l}$ forms identical mirror image due to presence of plane of symmetry.

$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]$ shows geometrical isomerism.