When carboxylic acid is treated with alcohol, is formed.

Which one of the following pairs gives effervescence with aq. $\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}{\mathrm{O}}_3$?

$$\begin{gathered} \underset{\left(\mathrm{I}\right)}{{\mathrm{CH}}_3\mathrm{COCl}} \underset{\left(\mathrm{II}\right)}{{\mathrm{CH}}_3{\mathrm{COCH}}_3} \\ \underset{\left(\mathrm{III}\right)}{{\mathrm{CH}}_3{\mathrm{COOCH}}_3} \underset{\left(\mathrm{IV}\right)}{{\mathrm{CH}}_3{\mathrm{COOCOCH}}_3} \end{gathered}$$