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 malignant tumors is radio resistant? 
Select and explain. 
A. Ewing Tumour, B. Retinoblastoma, C. Osteosarcoma, D. Neuroblastoma
C: Osteosarcoma
Answer: C: Osteosarcoma 
Explanation: None