Which of following organometallic compound is $\sigma$ and $\pi$ bonded : -

Question

( A ) $K[PtCl_3(\eta^2 – C_2H_4)]$
( B ) $[Fe(\eta^5 – C_5H_5)_2]$
( C ) $Fe(CH_3)_3$
( D ) $[Co(CO)_5NH_3] ^{+2}$