This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ohopedics Oncology, Subject name: Orthopaedics
[{'content': "Most radio-resistant tumor: \nSelect and explain. \nA. Osteosarcoma, B. Malignant fibrous histiocytoma, C. Ewing's sarcoma, D. Multiple myeloma", 'role': 'user'}, {'content': "Answer: A \nExplanation: Radio-resistant tumour: Osteosarcoma Chondrosarcoma Malignant fibrous histiocytoma Most radio-sensitive - Ewing's sarcoma", 'role': 'assistant'}]