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 substance emits the following except – \nSelect and explain. \nA. Gamma, B. Beta, C. Alpha, D. X–rays', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Linear accelerator:-\xa0X-ray, electron beam.\nRadioactive nuclide :-\xa0Gamma rays and particulate radiations (Alpha particles, Beta particles, Positrons, neutrons).', 'role': 'assistant'}]