Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is:

Susceptibility to nucleophilic attack depends on the magnitude of the positive charge on the carbonyl carbon and the leaving group ability.Acyl chlorides (${\text{CH}}_3\text{COCl}$) are the most reactive because:Chlorine is highly electronegative and strongly pulls electrons away from the carbonyl carbon via $-I$ effect.${\text{Cl}}^{-}$ is a very weak base and thus an excellent leaving group.Order of reactivity: Acyl chloride > Anhydride > Ester > Amide.