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': 'Variation in eruption in permanent dentition \nSelect and explain. \nA. 4-5 months, B. 7-9 months, C. 1-2 months, D. 12-18 months', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]