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
How long after completion of root of primary tooth ; root of primary tooth start to resorb 
Select and explain. 
A. 1 year approx, B. 2 year approx, C. 3 year approx, D. 4 year approx
C: 3 year approx
Answer: C: 3 year approx 
Explanation: None