a
(a) Amongst aldehyde and the acid derivatives, acid chloride are the most susceptible to nucleophilic attack due to strong \(-I\) effect and weak \(+R\) effect of the \(Cl-\)atom as a result of which carbonyl carbon has the highest electron deficiency.
The actual order is
\(MeCOCl >MeCOOCOMe >MeCOOMe >MeCHO.\)