Which of the following represents a strong acid?

Sulfuric acid is classified as a strong acid due to its complete dissociation in aqueous solutions. When sulfuric acid is added to water, it ionizes entirely to produce hydrogen ions (H⁺) and bisulfate ions (HSO₄⁻) in its primary dissociation step. In strong acids, this complete ionization is what leads to a significant concentration of hydrogen ions in solution, leading to lower pH levels.

In contrast, the other acids listed do not fully dissociate in water. Acetic acid, for example, is a weak acid that only partially ionizes, resulting in fewer hydrogen ions in the solution. Carbonic acid and phosphoric acid also have incomplete dissociation, meaning they do not contribute as many hydrogen ions compared to a strong acid like sulfuric acid. Therefore, sulfuric acid stands out as a strong acid due to its ability to generate a high concentration of hydrogen ions, making it particularly effective in acid-base reactions and other applications in chemistry.