Which of the following mixtures makes up a buffer solution? A. 10 mL 0.1 M NaOH & 20 mL 0.1 M HC2H3O2 B. 10 mL 0.1 M HCl & 10 mL 0.1 M NH4Cl C. 10 mL 0.1 M HCl & 20 mL 0.1 M HC2H3O2 D. 10 mL 0.1 M NaCl & 10 mL 0.1 M NH4Cl E. None of the choices