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: Orthopaedics
[{'content': "Not a diaphyseal tumor \nSelect and explain. \nA. Adamantinoma, B. Chondroblastoma, C. Osteoid osteoma, D. Ewing's sarcoma", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]