What is an example of a strong acid?

The correct choice, HBr (hydrobromic acid), is considered a strong acid because it completely dissociates in water to produce hydronium ions (H3O+) and bromide ions (Br-). This complete ionization in aqueous solution results in a high concentration of hydrogen ions, which is a defining characteristic of strong acids. Strong acids, including HBr, tend to have a lower pH and are very effective at donating protons (H+) to other compounds.

In contrast, the other options represent acids that do not fully dissociate in solution. For example, HNO2 (nitrous acid) is a weak acid, meaning it only partially ionizes in an aqueous solution. Similarly, HF (hydrofluoric acid) is also classified as a weak acid, despite being capable of causing severe damage; it does not fully dissociate in water. H2SO3 (sulfurous acid) is another weak acid, only partially dissociating into its ions. Thus, HBr stands out as a strong acid due to its complete ionization in solution, making it the correct choice.