Answer:
Buffers are substances that help resist shifts in pH by both donating H⁺ and accepting H⁺ (option D).
Explanation:
A buffer is a chemical substance capable of balancing the pH of a solution, when the balance is altered by the addition of an acid or a base. They are also called cushioning solution, and can be formed by an acid and its base conjugated, with a specific range of action.
The presence of a buffer in a solution has the ability to release hydrogen ions (H⁺) or accept them, helping to balance the pH, in the presence of a base or an acid, respectively. That is, a buffer can yield H⁺ to a solution when there are few or accept H⁺ when its content is high.
The other options are not correct because:
A. Buffers do not release H+ into a solution when acids are added, but accept them.
B and C. Giving up H+ to a solution when bases are added or accepting H+ from a solution when acids are added are effects that buffers can potentially do, which is described in the text above.
