This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which is the only amino acid with good buffering capacity at physiological pH? 
Select and explain. 
A. Arginine, B. Glutamic acid, C. Histidine, D. Valine
C: Histidine
Answer: C: Histidine 
Explanation: Histidine plays a key role in making hemoglobin an excellent buffer in red blood cells.