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': 'How long after completion of root of primary tooth ; root of primary tooth start to resorb \nSelect and explain. \nA. 1 year approx, B. 2 year approx, C. 3 year approx, D. 4 year approx', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]