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
The levels of nicotine in 6 cigarettes were 13.0, 11.8,
15.4, 17.4, 31.2 and 24.3 mg. The mean of these values is 
Select and explain. 
A. 14.9, B. 15.9, C. 18.6, D. 8.4
C: 18.6
Answer: C: 18.6 
Explanation: None