Identify neutral ligand from following?

Neutral ligand identification

A neutral ligand donates an electron pair without carrying net charge. Among the options:

Carbonyl ($\mathrm{CO}$) is neutral, as in $\mathrm{Ni(CO)_4}$ or $\mathrm{Fe(CO)_5}$.
Sulphato ($\mathrm{SO_4^{2-}}$), oxalato ($\mathrm{C_2O_4^{2-}}$), and bromo ($\mathrm{Br-}$) are anionic.

Only carbonyl qualifies as neutral.

Final answer: $\boxed{\text{A}}$