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': 'Root completion in primary teeth is by the age of \nSelect and explain. \nA. 1 - 3years, B. 5 -6 years, C. 3 - 4 years, D. 7 -8 years', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]