Which definition best describes a buffer? a. a substance in a solution that captures hydrogen ions and raises the ph b. a substance in a solution that releases hydrogen ions and lowers the ph c. a substance in a solution that releases and captures hydrogen ions, keeping the ph the same d. a substance in a solution that changes color in a narrow range of ph?

             Option-C (A substance in a solution that releases and captures hydrogen ions, keeping the pH the same) is the correct answer.

Explanation:
                   Buffer solutions are those solutions which tends to resist the change in pH when a small amount of acid or base is added to it. So, when a base is added it donates proton to neutralize it, and when an acid is added it captures the proton of acid to neutralize it.
                   Buffer solutions are made of weak acid and salt of conjugate base of that weak acid or are made up of weak base and salt of conjugate acid of that base.

Example:
                               CH₃COOH / CH₃COO⁻ Na⁺