Which method(s) can be used to determine the concentration of ${\mathrm{HNO}}_3$ in an aqueous solution of nitric acid?

(P) Titration with a standard base
(Q) Titration with a standard oxidizing agent
(R) Precipitation with ${\mathrm{Ag}}^{+}$

However, Raman spectroscopy should be used if you want to determine whether nitric acid, or the undissociated acid$\mathit{ }HN{O}_{\mathit{3}}$, is present.

Sulphur acid in diluted form is the acid employed in this titration. Hydrochloric acid is typically avoided because it combines with ${\mathrm{KMnO}}_4$ in accordance with the equation provided below to create chlorine and chlorine, which is also an oxidizing agent in the aqueous solution. Nitric acid is not used since it is itself an oxidizing agent.

Hence, option A is correct.