Which of the following sentence best describes a buffer?

A. Buffers resist change in pH of solutions by neutralizing excess acid or base.

B. Buffers change the pH of solutions by increasing acidity or basicity of solutions. C. Buffers change the pH of solutions by decreasing acidity or basicity of solutions.

The answer is A. Buffers resist change in pH of solutions by neutralizing excess acid or base.

Here is an explanation: A buffer is an acid-base solution that has a weak acid and a weak base in equilibrium (balance) and they're conjugates of each other. For example, adding new acids would have it react with the conjugate base to keep the pH up (since acids bring the pH drastically down in a non-buffer). It is the same with an added base: adding a new base would have it react with the conjugate acid to keep the pH down.