The correct option is C CH3COOH
The electrophilicity of carbonyl carbon of aldehyde is more than ketone because in ketone two R groups will minimise the electrophilicity due to inductive effect. But the electrophilicity of carboxylic carbon is greatly diminished due to resonance, thus the electrophilicity is least in case of carboxylic carbon. Hence CH3COOH will be least reactive towards nucleophilic addition reaction.