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
The fraction of inspired air in mouth-to-mouth respiration is: 
Select and explain. 
A. 0.16, B. 0.19, C. 0.21, D. 0.26
A: 0.16
Answer: A: 0.16 
Explanation: A i.e. 0.16Mouth - to mouth respiration provides 16% of 02.In mouth- to - mouth respiration the resuscitor takes a deep breath & exhales into the subject's mouth. It provides 16% (15.7%) of 02.(amount of 02 that is present in expired air)