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: Surgery
[{'content': 'Distraction osteogenesis can be performed as early as? \nSelect and explain. \nA. 2 years of age, B. 4 years of age, C. 6 years of age, D. 8 years of age', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]