Which of the Following Solutions Will Be the Best Buffer $\times$

Multiple Choice

Which of the following solutions will be the best buffer at a pH of 9.26? (K_a for HC₂H₃O₂ is 1.8 $\times$ 10^-5,K_b for NH₃ is 1.8 $\times$ 10^-5) .

A) 0.10 M HC₂H₃O₂ and 0.10 M Na C₂H₃O₂
B) 5.0 M HC₂H₃O₂ and 5.0 M Na C₂H₃O₂
C) 0.10 M NH₃ and 0.10 M NH₄Cl
D) 5.0 M NH₃ and 5.0 M NH₄Cl
E) 5.0 M HC₂H₃O₂ and 5.0 M NH₃