Stronger the field strength of ligand, higher will be the energy absorbed by the complex. ⇒ 'en' has a stronger field strength than ' H2O ' according to spectrochemical series ∴ Correct order of energy absorbed will be: [Ni(en)3]2+>[Ni(H2O)2(en)2]2+>[Ni(H2O)4(en)]2+ i.e. (C)>(A)>(B)