In which of the following co-ordination entities the magnitude of $\bigtriangleup_o$ (CFSE in octahedral field) will be maximum? <br> (Atomic number of Co=27)

Question

( A ) $[Co(CN)_6]^{3-}$
( B ) $[Co(NH_3)_6]^{3+}$
( C ) $[Co(C_2O_4)_3]^{3-}$
( D ) $[Co(H_2O)_6]^{3+}$