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': 'When are the crowns of the primary maxillary second molars completed? \nSelect and explain. \nA. 11 months., B. 10 months., C. 9 months., D. 8 months.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]