What is a key difference between diprotic and monoprotic buffers?

• A. Monoprotic buffers have two pK_a values.
• B. Monoprotic buffers can only exist in acidic solutions.
• C. Diprotic buffers have two acidic hydrogens and two pK_a values.
• D. Diprotic buffers have only one acidic hydrogen.

Answer: (C)