All of the Following Solutions Are Buffers EXCEPT

All of the following solutions are buffers EXCEPT

A) 100 mL of 0.500 M H₂PO₄− added to 100 mL of 0.200 M HPO₄²⁻.
B) 100 mL of 0.200 M HF added to 200 mL of 0.200 M NaF.
C) 200 mL of 0.200 M HCl added to 200 mL of 0.400 M CH₃CO₂−.
D) 200 mL of 0.500 M NaOH added to 200 mL of 1.000 M HF.
E) 200 mL of 0.400 M HCl added to 100 mL of 0.200 M CH₃CO₂−.