All of the following solutions form a buffer except:
I. 1.0 M H₂CO₃ and 1.0 M NaHCO₃
II. 1.0 M CH₃NH₂ and 1.0 M CH₃NH₃Cl
III. 1.0 M NaOH and 1.0 M HBr
IV. 1.0 M CH₃NH₂ and 1.0 M HBr
V. 1.0 M H₃PO₄ and 1.0 M NaH₂PO₄

• A. I and V
• B. III and IV
• C. III and V
• D. I and IV

Answer: (C)