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: Physiology
Slowest acting buffer system in the body ? 
Select and explain. 
A. PCO, buffer, B. Respiratory buffer, C. Chemical buffer, D. Renal buffer
D: Renal buffer
Answer: D: Renal buffer 
Explanation: Ans. is 'd' i.e., Renal buffer(Re/ Principles of medical physiology p. 712)Not all buffer systems begin work at the same time.Chemical buffers respond first, followed by the respiratory system and finally, the renal system.