Which of the following is a strong electrolyte?

The correct answer is a) sulfuric acid.

Strong electrolytes are substances that completely dissociate into ions in solution, leading to high conductivity. Sulfuric acid (H₂SO₄) is a strong acid that fully ionizes in water, breaking down into hydrogen ions (H⁺) and sulfate ions (SO₄^2-).

On the other hand, sulfurous acid (H₂SO₃), ammonia (NH₃), and acetic acid (CH₃COOH) are considered weak electrolytes as they do not fully dissociate in solution. Sulfurous acid partially ionizes, while ammonia acts as a weak base, and acetic acid only partially dissociates to form acetate ions (CH₃COO^–). Therefore, among the given options, only sulfuric acid qualifies as a strong electrolyte.