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
At what age root resorption start 
Select and explain. 
A. 5 years, B. 3 years, C. 6.5 years, D. 7 years
A: 5 years
Answer: A: 5 years 
Explanation: 1st to resorb is Mandibular central incisor start resorbing at 5 years of age