Explanation

A polyprotic acid is an acid that can donate more than one proton (H⁺) per molecule.

1. H₃PO₄ (Phosphoric acid) → Triprotic acid (can donate 3 H⁺ ions)
2. HCN (Hydrocyanic acid) → Monoprotic (donates only 1 H⁺)
3. HCl (Hydrochloric acid) → Monoprotic