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': "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 highly radio resistant.', 'role': 'assistant'}]