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': 'The upper limit of safety for carbon monoxide in air is - \nSelect and explain. \nA. 0.20%, B. 0.01%, C. 0.40%, D. 0.01%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The upper limit of safety of CO in air is 0.01%.', 'role': 'assistant'}]