Among the complex ions, $\left[\mathrm{Co}\left(\mathrm{NH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NH}_2\right)_2 \mathrm{Cl}_2\right]^{+},\left[\mathrm{CrCl}_2\left(\mathrm{C}_2 \mathrm{O}_4\right)_2\right]^{3-},\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_4(\mathrm{OH})_2\right]^{+}$, $\left[\mathrm{Fe}\left(\mathrm{NH}_3\right)_2(\mathrm{CN})_4\right]^{-},\left[\mathrm{Co}\left(\mathrm{NH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NH}_2\right)_2\left(\mathrm{NH}_3\right) \mathrm{Cl}\right]^{2+}$ and $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_4\left(\mathrm{H}_2 \mathrm{O}\right) \mathrm{Cl}\right]^{2+}$, the number of complex ion(s) that show(s) cis-trans isomerism is