If a Small Amount of a Strong Base Is Added

If a small amount of a strong base is added to buffer made up of a weak acid, HA,And the sodium salt of its conjugate base,NaA,The pH of the buffer solution does not change appreciably because

A) the K_a of HA is changed.
B) No reaction occurs.
C) the strong base reacts with A^- to give HA, which is a weak acid.
D) the strong base reacts with HA to give AOH and H⁺.
E) the strong base reacts with HA to give A^-, which is a weak base.