Which of the following compounds show optical isomerism?

(P) $\text{ cis- }{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]}^{+}$ (Q) $\text{ trans- }{\left[\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]}^{+}$

(R) $\text{ cis- }{\left[\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]}^{+}$ (S) ${\left[\mathrm{Co}(en{)}_3\right]}^{3+}$

Select the correct answer using the codes given below: