A buffer solution is prepared from equimolar amounts of acetic acid, CH₃COOH, and its conjugate base, CH₃COO⁻(aq). When a small amount of aqueous NaOH is added to this buffer, which species in the solution reacts directly with the added OH⁻ ions?
a) CH3COO−(aq)
b) CH3COOH(aq)
c) H3O+(aq)
d) H2O(l)