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
Which of the following is the principal buffer in interstitial fluid? 
Select and explain. 
A. Hemoglobin, B. Other proteins, C. H2CO3, D. H2PO4
C: H2CO3
Answer: C: H2CO3 
Explanation: Principal buffers in the body: