Which among the following is NOT dicarboxylic acid?

Identify ' $A$ ' in the following reaction.

A + Acetic anhydride $\xrightarrow{\mathrm{H}^{+}}$Aspirin + Acetic acid

$$ \mathrm{S} \xrightarrow{\text { Dimethylcadmium }} \text { Propanone }+ \text { Cadmium chloride } $$

In a reaction,

$$ \left(\mathrm{CH}_3\right)_2 \mathrm{CHMgBr}+\mathrm{CO}_2 \xrightarrow[\text { ether }]{\text { dry }} \mathrm{A} \xrightarrow[\text { dilHCl }]{\mathrm{H} . \mathrm{OH}} \mathrm{~B} \text {. } $$

Find the product ' B ' of above reaction.