This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 2, Subject name: Physiology
Normal pO2 in venous blood is: 
Select and explain. 
A. 40 mmHg, B. 60 mmHg, C. 80 mmHg, D. 95 mmHg
A: 40 mmHg
Answer: A: 40 mmHg 
Explanation: pO2 of the aerial blood = 95 mmHg pO2 of venous blood = 40 mmHg pCO2 of the aerial blood = 40 mmHg pCO2 of venous blood = 45 mmHg