The complex ion that will lose its crystal field stabilization energy upon oxidation of metal to +3 state is:

(Phen = phenanthroline, ignore pairing energy)

A

[Ni(phen)$$_3$$]$$^{2+}$$

B

[Fe(phen)$$_3$$]$$^{2+}$$

C

[Co(phen)$$_3$$]$$^{2+}$$

D

[Zn(phen)$$_3$$]$$^{2+}$$