Hydrolysis of an ester gives a carboxylic acid, which on Kolbe's electrolysis, yields ethane. The ester is:

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

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{COOH}\underset{\mathrm{red} \mathrm{P}}{\overset{{\mathrm{Cl}}_2}{\to }}\mathrm{A}\stackrel{\text{ alc.KOH }}{⟶}\mathrm{B}.$

What is $\mathrm{B}?$

Which of the following decolourises the colour of acidic ${\mathrm{KMnO}}_4$?

Reagent may be -