Final answer:
The combination that cannot produce a buffer solution is NH₃ and (NH₄)₂SO₄.
Step-by-step explanation:
The combination that cannot produce a buffer solution is option d. NH₃ and (NH₄)2SO₄.
A buffer solution is a solution that can resist changes in pH when a small amount of acid or base is added to it. In order for a solution to act as a buffer, it requires a weak acid and its conjugate base, or a weak base and its conjugate acid.
In option d, NH₃ is a weak base, but (NH₄)2SO₄ is a salt made from a strong acid and a weak base. Therefore, this combination cannot produce a buffer solution.