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': 'A six-year molar begins to calcify at: \nSelect and explain. \nA. Six months IU, B. At birth, C. 1 year after birth, D. 3 years age', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]