Among the following complexes the one which shows Zero crystal field stabilizations energy (CFSE) :

Question

( A ) $[Co(H_2O)_6]^{2+}$
( B ) $[Co (H_2O)_6]^{3+}$
( C ) $[Fe(H_2O)_6]^{3-}$
( D ) $[Mn (H_2O)_6]^{3+}$