This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concepts in physiology, Subject name: Physiology
[{'content': 'Which of the following is the principal buffer in interstitial fluid? \nSelect and explain. \nA. Hemoglobin, B. Other proteins, C. H2CO3, D. H2PO4', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Principal buffers in the body:', 'role': 'assistant'}]