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
[{'content': 'O2 which is about 21% of inspired air exerts a partial pressure of \nSelect and explain. \nA. 160 mmHg, B. 240mmHg, C. 580mmHg, D. 760mmHg', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In inspired air, partial pressure of O2- 158mmHg', 'role': 'assistant'}]