Which of the following is an example of a strong acid?

Hydrochloric acid is classified as a strong acid because it completely dissociates in water to produce hydrogen ions (H⁺) and chloride ions (Cl⁻). This complete dissociation is a key characteristic of strong acids, which contrasts with weak acids, like acetic acid, sulfurous acid, and citric acid, that do not fully dissociate in solution and typically exist in an equilibrium between undissociated molecules and ions. This property is significant because strong acids have a lower pH and a greater ability to donate protons compared to weak acids, making them much more reactive in typical chemistry scenarios.