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
Most radio-resistant tumor: 
Select and explain. 
A. Osteosarcoma, B. Malignant fibrous histiocytoma, C. Ewing's sarcoma, D. Multiple myeloma
A: Osteosarcoma
Answer: A: Osteosarcoma 
Explanation: Radio-resistant tumour: Osteosarcoma Chondrosarcoma Malignant fibrous histiocytoma Most radio-sensitive - Ewing's sarcoma