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
[{'content': "Which of the following is not sensitive to radiotherapy? \nSelect and explain. \nA. Ewings sarcoma, B. Osteosarcoma, C. Wilms', D. Neuroblastoma", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Osteosarcoma', 'role': 'assistant'}]