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': 'Which of the following is the first target of distraction force? \nSelect and explain. \nA. Osteoclasts, B. Osteoblasts, C. Mononuclear cells, D. Endothelial cells', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]