The reaction of aniline with ${\mathrm{HNO}}_2$ followed by treatment of dilute acid gives.

 The reaction of aniline with ${\mathrm{HNO}}_2$ followed by treatment of dilute acid gives ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$. 

Aniline reacts similarly to primary aliphatic amines. Aniline gives diazonium ion after treatment with nitrous acid. On further treatment with dilute acid undergo hydrolysis reaction. Aromatic diazonium ion is a very important intermediate to produce substituted benzene. 

The final product depends on reagent use. Here the reagent used is dilute acid so the diazonium ion undergoes a hydrolysis reaction. The addition of water molecules is known as the hydrolysis reaction. Amines on hydrolysis give alcohol as the product while aniline gives phenol as the product. 

Hence, the correct answer is option B) ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$.