An ammonium buffer solution is prepared by combining 50. mL of 0.20 M ammonia, NH3(aq), and 50. mL of 0.20 M of ammonium chloride, NH4Cl(aq). A 5.0 mL sample of 0.10 M HCl(aq) is added to the buffer solution. Which of the following is a correct pairing of the ammonium species present in greater concentration and of the pH of the solution after the HCl(aq) is added? (The pKb of ammonia is 4.7.)

(A) NH3 < 9.3
(B) NH3 > 9.3
(C) NH4+ < 9.3
(D) NH4+ > 9.3