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
Central Chemoreceptors are most sensitive to following changes in blood: 
Select and explain. 
A. T PCO2, B. I PCO2, C. TH+, D. T PO2
A: T PCO2
Answer: A: T PCO2 
Explanation: T PCO2