Explanation:

Strong acids completely dissociate in water, releasing all of their hydrogen ions (H+). NaOH is a strong base, HF is a weak acid, and NH3 is a weak base. Therefore, HCl is the only strong acid among the given options.

Here are the dissociation reactions for each substance in water:

- NaOH: NaOH(aq) → Na+(aq) + OH-(aq)

- HF: HF(aq) ⇌ H+(aq) + F-(aq)

- NH3: NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

- HCl: HCl(aq) → H+(aq) + Cl-(aq)