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: Pharmacology
[{'content': 'To minimize the effects of diffusion hypoxia during N2O-O2 analgesia, the patient should be oxygenated for \nSelect and explain. \nA. 30 seconds to 1 minutes, B. 3 to 5 minutes, C. 10 to 30 minutes, D. 30 to 45 minutes', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]