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
What is the longest duration of function of primary teeth 
Select and explain. 
A. 6 yr, B. 8 yr, C. 10 yr, D. 12 yr
C: 10 yr
Answer: C: 10 yr 
Explanation: None