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': 'Radioactive emissions used in radiotherapy are \nSelect and explain. \nA. Gamma rays, B. Alpha particles, C. Beta particles, D. X-ray', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]