Coordination Compounds

The correct statements about metal carbonyls are

A. The metal-carbon bonds in metal carbonyls possess both $\sigma$ and $\pi$ character.

B. Due to synergic bonding interactions between metal and CO ligand, the metal-carbon bond becomes weak.

C. The metal-carbon $\sigma$ bond is formed by the donation of lone pair of electrons on the carbonyl carbon into a vacant orbital of metal.

D. The metal-carbon $\pi$ bond is formed by the donation of electrons from filled d-orbital of metal into vacant $\pi^*$ orbital of CO .

Choose the correct answer from the options given below :