Which one of the following esters cannot undergo Claisen self-condensation?

In a set of reactions, propionic acid yielded a compound $\mathrm{D}$.

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{COOH}\stackrel{{\mathrm{SOCl}}_2}{⟶}\mathrm{B}\stackrel{{\mathrm{NH}}_3}{\to }\mathrm{C}\underset{{\mathrm{Br}}_2}{\overset{\mathrm{KOH}}{\to }}\mathrm{D}$

The structure of $\mathrm{D}$ would be