Answer:
a weak acid and its conjugate base
Explanation:
A Buffer solution is a solution that tends to keep the pH almost constant when small amounts of acids (H +) or bases (OH-) are added, therefore, they are very useful to reduce the impact of drastic changes in (H+) and (OH-) in processes that require a specific pH. They can be prepared by dissolving in water adequate amounts of a weak acid and a salt of its conjugate base, or a weak base and a salt of its conjugate acid.