Which One of the Following Is a Buffer Solution

Multiple Choice

Which one of the following is a buffer solution

A) 0.40 M HCN and 0.10 KCN
B) 0.20 M CH₃COOH
C) 1.0 M HNO₃ and 1.0 M NaNO₃
D) 0.10 M KCN
E) 0.50 M HCl and 0.10 NaCl