Which one of the following metal complexes is most stable? [JEE Main 2021, 25 Jul (Shift 2)]

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

\(\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2\)

\(\left[\mathrm{Co}(\mathrm{en})_3\right] \mathrm{Cl}_2\)

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