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': 'Symptoms of CO poisoning stas when the concentration is: \nSelect and explain. \nA. < 10%, B. > 10%, C. > 20 %, D. > 40 %', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. > 10%', 'role': 'assistant'}]