The aqueous solution of which of the following can form buffer solution?

Explanation

A buffer solution is formed by a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid. In option A, HF (weak acid) and NaF (conjugate base) can form a buffer. Option B, NH₃ (weak base) and NH₄Cl (conjugate acid) also form a buffer. Similarly, in option C, CO₃²⁻ and Na₂CO₃ form a buffer system with CO₃²⁻ acting as the base and HCO₃⁻ (from Na₂CO₃) as the acid. Therefore, option D, 'All of these,' correctly indicates that all pairs can form buffer solutions.