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: Dental
[{'content': 'The levels of nicotine in 6 cigarettes were 13.0, 11.8,\n15.4, 17.4, 31.2 and 24.3 mg. The mean of these values is \nSelect and explain. \nA. 14.9, B. 15.9, C. 18.6, D. 8.4', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]