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
To keep blood pH at 7.4, the HCO3 : H2CO3 ratio should be 
Select and explain. 
A. 20:01, B. 30:01:00, C. 15:01, D. 1:01
A: 20:01
Answer: A: 20:01 
Explanation: None