An acetic acid buffer containing 0.50 M CH₃COOH and 0.50 M CH₃COONa has a pH of 4.74. What will the pH be after 0.0020 mol of HCI has been added to 100.0 mL of the buffer?
A) 4.77
B) 4.71
C) 4.68
D) 4.62
E) none of the above