Which of the following cannot act both as Bronsted acid and as...

Key Idea Bronsted acid is a substance which has a tendency to donate proton. Bronsted base is a substance which has a tendency to accept proton. HCl can act as Bronsted acid becuase it can only donate proton. $\mathrm{HCl}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{H}_{3}$ \mathrm{O}^{+}+$\mathrm{Cl}^{-}The remaining options contains substances which act both as Bronsted acid$ and Bronsted base.$$\begin{aligned}\mathrm{HCO}_{3}^{-}+ \mathrm{HCO}_{3}^{-} & \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}+\mathrm{CO}_{3}^{2-} \\ \mathrm{NH}_{3}+\mathrm{NH}_{3}& \rightleftharpoons \mathrm{NH}_{4}^{+}+\mathrm{NH}_{2}^{-} \\ \mathrm{HSO}_{4}^{-}+\mathrm{HSO}_{4}^{-} & \rightleftharpoons \mathrm{H}_{2}\mathrm{SO}_{4}+\mathrm{SO}_{4}^{2-} \end{aligned}$$ Thus, option (3) is correct.