The correct order of energy of absorption for the following metal complexes is A:[ Ni ( en )_3]^2+, B:[ Ni ( NH_3)_6]^2+, C:[ Ni ( H_2 O )_6]^2+

The correct order of energy of absorption for the following metal complexes is $\displaystyle \mathrm{A}:\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}, \mathrm{B}:\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+}, \mathrm{C}:\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$