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: Unknown
Partial pressure of CO2 is lowest in: 
Select and explain. 
A. Arterial blood, B. End tidal air, C. Expired air, D. Venous blood
C: Expired air
Answer: C: Expired air 
Explanation: (Refer: Ganong Figure 34-15, 24th edition, pg no: 635)
Normal P02 and PC02 at various sites