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': '1st evidence of calcification of Mandibular 1st molar is seen in \nSelect and explain. \nA. At birth, B. 9-10 years, C. 11-12 years, D. 8-9 years', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]