Which of the following derivatives of alcohols is unstable in an aqueous base?

The increasing order of the reactivity of the following compounds in nucleophile addition reaction is:

Propanal, Benzaldehyde, Propanone, Butanone

The compound A in the following reactions is:

$$\begin{gathered} \mathrm{A} \underset{\left(\mathrm{ii}\right) \mathrm{Conc}. {\mathrm{H}}_2{\mathrm{SO}}_4/∆}{\overset{\left(\mathrm{i}\right) {\mathrm{CH}}_3\mathrm{MgBr}/{\mathrm{H}}_2\mathrm{O}}{\to }} \\ \mathrm{B} \underset{\left(\mathrm{ii}\right) \mathrm{Zn}/{\mathrm{H}}_2\mathrm{O}}{\overset{\left(\mathrm{i}\right) {\mathrm{O}}_3}{\to }}\mathrm{C}+\mathrm{D} \end{gathered}$$