The solution that will have the greatest number of H₃O⁺ ions at equilibrium is the strong acid.
Strong acids completely dissociate in water, producing a high concentration of H₃O⁺ ions. In contrast, weak acids only partially dissociate, and weak bases will produce fewer H₃O⁺ ions as they accept protons instead of contributing to their concentration. Thus, among the options provided, the strong acid will yield the most H₃O⁺ ions in solution.