This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification of Bone Tumors, Subject name: Orthopaedics
[{'content': "Which one of the following bone tumors typically affects the epiphysis of a long bone? \nSelect and explain. \nA. Osteosarcoma, B. Ewing's sarcoma, C. Chondroblastoma, D. Chondromyxoid fibroma", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is \'c\' ie chondroblastoma (Ref: Apley\'s, 8/e, p177).Apley\'s - "X-Ray shows a rounded, well demarcated radiolucent area in the epiphysis; this site is so unusual that the diagnosis springs readity to mind; However, sometimes the lesion extends across the physeal line".Remember', 'role': 'assistant'}]