In the following sequence of reactions

${\mathrm{CH}}_3\mathrm{Br}\stackrel{\mathrm{KCN}}{⟶}\mathrm{A}\stackrel{{\mathrm{H}}_3{\mathrm{O}}^{+}}{⟶}\mathrm{B}\stackrel{{\mathrm{LiAlH}}_4}{⟶}$, The end product C is

The reaction,

${\mathrm{CH}}_3\mathrm{Br}\stackrel{\mathrm{KCN}}{\to }{\mathrm{CH}}_3-\underset{\mathrm{A}}{\mathrm{C}}\mathrm{N}\stackrel{{\mathrm{H}}_3{\mathrm{O}}^{+}}{\to }{\mathrm{CH}}_3-\underset{\mathrm{B}}{\mathrm{COOH}}\stackrel{{\mathrm{LiAlH}}_4}{\to }{\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{OH}$

Acetonitrile is created when methyl bromide and $\mathrm{KCN}$ react with each other. $\mathrm{CN}$ group is used to replace the $\mathrm{Br}$ atom. Cyano group hydrolysis produces a carboxylic group. Hydroxyl group is produced when a carboxylic group is reduced.

Hence, the correct answer is option (B) Ethyl alcohol.