The solution that will have the greatest number of H3O+ ions at equilibrium is:
strong acid
Strong acids completely dissociate in water, producing a high concentration of H3O+ ions. In contrast, weak acids only partially dissociate, and strong bases will lead to a decrease in H3O+ ions due to the formation of OH- ions. Weak bases also do not produce H3O+ ions in significant amounts. Therefore, strong acids contribute the most H3O+ ions in solution.