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': 'What is the longest duration of function of primary teeth \nSelect and explain. \nA. 6 yr, B. 8 yr, C. 10 yr, D. 12 yr', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]