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 malignant tumors is radioresistant? \nSelect and explain. \nA. Ewing's sarcoma, B. Retinoblastoma, C. Osteosarcoma, D. Neuroblastoma", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Osteosarcoma is a radioresistant tumor; therefore treatment focuses on chemotherapy and surgery. Ref: Encyclopedia of Cancer, Volume 1, By Manfred Schwab, 2008, Page 2201; Aicle: Pahenolide and Ionizing Radiation Synergistically Induce Cell Death in LM7 Osteosarcoma Cells, 2012.', 'role': 'assistant'}]