If a didentate ligand ethane-1, 2-diamine is progressively added in the molar ratio en : \(\mathrm{Ni}\) \(:: 1: 1,2: 1,3: 1\) to \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\) aq solution, following co-ordination entities are formed.
I. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_4 \mathrm{en}\right]^{2+}(a q)-\) pale blue
II. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_2(\mathrm{en})_2\right]^{2+}(a q)-\) blue/purple
III. \(\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}(\mathrm{aq})\) - violet
The wavelength in \(\mathrm{nm}\) of light absorbed in case of I and III are respectively

1. A \(475 \mathrm{~nm}\) and \(310 \mathrm{~nm}\)
2. B \(300 \mathrm{~nm}\) and \(475 \mathrm{~nm}\)
3. C \(310 \mathrm{~nm}\) and \(500 \mathrm{~nm}\)
4. D \(600 \mathrm{~nm}\) and \(535 \mathrm{~nm}\)