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: Forensic Medicine
[{'content': 'To what extent must the oxygen content be reduced before an explosion of methane and air is impossible? \nSelect and explain. \nA. 12 percent, B. 10 percent, C. 11 percent, D. 7 percent', 'role': 'user'}, {'content': 'Answer: A \nExplanation: For a mixture of strictly methane and air, the oxygen content must be 12 percent or less.\xa0\nIt is however, significant to note that there is a combination of combustible gases following explosions and during fires.\nSo the maximum allowable oxygen will vary according to variations in the combustible and inert gases.', 'role': 'assistant'}]