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': 'Optimum rate of movement during distraction osteogenesis is \nSelect and explain. \nA. 1 mm per day, B. 5 mm per day, C. 1 cm per week, D. 5 cm per week', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]