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: Medicine
CPR should have a ratio of chest compression to mouth breathing of: 
Select and explain. 
A. 1:04, B. 4:01, C. 2:03, D. 3:02
B: 4:01
Answer: B: 4:01 
Explanation: None