$\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{H}_{2} \mathrm{NO}_{3}^{+}+\mathrm{HSO}_{4}^{-}$
$\mathrm{H}_{2} \mathrm{NO}_{3}^{+} \rightarrow \mathrm{NO}_{2}^{+}+\mathrm{H}_{2} \mathrm{O}$
Hence, in this reaction HNO $_{3}$ acts as a base and $\mathrm{H}_{2} \mathrm{SO}_{4}$ as an acid.


$A\,and\,C\,\xrightarrow{{{\text{Diazotization}}}}\,P + Q\,\xrightarrow[{(ii)\,oxidation\,\left( {KMn{O_4} + {H^ + }} \right)}]{{{\text{(i) Hydrolysis}}}}$$\begin{array}{*{20}{c}} {R\left( {product\,of\,A} \right)} \\ { + \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ {s\,\left( {prosuct\,of\,C} \right)} \end{array}$