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: Radiology
Which of the following tumor is least radiosensitive hence it is ineffective for radiotherapy? 
Select and explain. 
A. Ewing's sarcoma, B. Osteosarcoma, C. Wilms tumor, D. Neuroblastoma
B: Osteosarcoma
Answer: B: Osteosarcoma 
Explanation: Osteosarcoma is radioresistant; radiation therapy has no role in the routine management. Preoperative chemotherapy followed by limb-sparing surgery (which can be accomplished in >80% of patients) followed by postoperative chemotherapy is standard management. Ref: Patel S.R., Benjamin R.S. (2012). Chapter 98. Soft Tissue and Bone Sarcomas and Bone Metastases. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.