This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
[{'content': 'Following are spontaneous resolution tumours except - \nSelect and explain. \nA. Malignant melanoma, B. Osteogenic sarcoma, C. Cholangio carcinoma, D. Retinoblastoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A cancer that stas in the bone. In the ends of bone where new bone forms as the person grows. Thigh, upper arm, shin are the common sites.', 'role': 'assistant'}]