The acyl derivatives $\mathrm{CH}{}_3\mathrm{COCl}$, $(\mathrm{CH}{}_3\mathrm{CO}{)}_2\mathrm{O}$, $\mathrm{CH}{}_3\mathrm{COOC}{}_2\mathrm{H}{}_5$ and $\mathrm{CH}{}_3\mathrm{CONH}{}_2$ release the leaving groups $\mathrm{Cl}{}^{-}$, $\mathrm{CH}{}_3\mathrm{COO}{}^{-}$, $\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{O}{}^{-}$ and $\mathrm{NH}{}_2{}^{-}$ in the second step of nucleophilic acyl substitution. The conjugate acids have pKa about -7, 4.76, 16 and 35 respectively. Considering leaving-group ability and resonance donation to the carbonyl, the order of reactivity toward nucleophiles is

1. A$\mathrm{CH}{}_3\mathrm{COCl}>(\mathrm{CH}{}_3\mathrm{CO}{)}_2\mathrm{O}>\mathrm{CH}{}_3\mathrm{COOC}{}_2\mathrm{H}{}_5>\mathrm{CH}{}_3\mathrm{CONH}{}_2$
2. B$(\mathrm{CH}{}_3\mathrm{CO}{)}_2\mathrm{O}>\mathrm{CH}{}_3\mathrm{COCl}>\mathrm{CH}{}_3\mathrm{COOC}{}_2\mathrm{H}{}_5>\mathrm{CH}{}_3\mathrm{CONH}{}_2$
3. C$\mathrm{CH}{}_3\mathrm{COCl}>\mathrm{CH}{}_3\mathrm{COOC}{}_2\mathrm{H}{}_5>(\mathrm{CH}{}_3\mathrm{CO}{)}_2\mathrm{O}>\mathrm{CH}{}_3\mathrm{CONH}{}_2$
4. D$\mathrm{CH}{}_3\mathrm{CONH}{}_2>\mathrm{CH}{}_3\mathrm{COOC}{}_2\mathrm{H}{}_5>(\mathrm{CH}{}_3\mathrm{CO}{)}_2\mathrm{O}>\mathrm{CH}{}_3\mathrm{COCl}$