Final answer:
The strong acid among the given options is HClO₄ (perchloric acid). HClO₄ is a strong acid because it completely dissociates into H⁺ ions and ClO₄⁻ ions in water.
Step-by-step explanation:
The strong acid among the given options is HClO₄ (perchloric acid). A strong acid is one that completely ionizes in water, resulting in the formation of hydronium ions (H₃O⁺). HClO₄ is a strong acid because it completely dissociates into H⁺ ions and ClO₄⁻ ions in water:
HClO₄ → H⁺ + ClO₄⁻
On the other hand, HF, KOH, H₃PO₄, and H₂CO₃ are weak acids. Weak acids only partially ionize in water, resulting in the formation of hydronium ions (H₃O⁺) and the undissociated acid species. Therefore, the correct answer is (c) HClO₄.