Coordination Compounds

Which of the following complexes exhibit geometrical isomerism?

I. $\left[\mathrm{Co}(\mathrm{en})\left(\mathrm{NH}_3\right)_2 \mathrm{Cl}_2\right] \mathrm{Cl}$

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

III. $\left[\mathrm{Co}(\mathrm{en})_3, \mathrm{Cl}_3\right.$

IV. $\left[\mathrm{Co}(\mathrm{en})_2 \mathrm{Cl}_2\right] \mathrm{Br}$