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': "A 19 yrs old male has a small circumscribed sclerotic swelling over diaphysis of femur, likely diagnosis is: \nSelect and explain. \nA. Osteoclastoma, B. Osteosarcoma, C. Ewing's sarcoma, D. Osteoid osteoma", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Sclerotic lesion over diaphysis of a long bone in a young patient indicative of osteoid osteoma. Ref: Essential Ohopedics By Maheshwari 2nd Edition, Page 213', 'role': 'assistant'}]