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
Most impoant buffer in interstitial fluid: 
Select and explain. 
A. Phosphate, B. Bicarbonate, C. Histidine, D. Protein
B: Bicarbonate
Answer: B: Bicarbonate 
Explanation: Principal buffers in body fluids: Blood H2CO3 = H+ + HCO3-HProt complex = H+ + Prot-HHb= H+ + Hb- Interstitial fluid H2CO3=H+ + HCO3- Intracellular fluid HProt complex = H+ + Prot-H2PO4- = H+ + HPO42-