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': 'X-rays are a type of \nSelect and explain. \nA. Atomic radiation, B. Ultrasonic radiation, C. Electromagnetic radiation, D. Particulate radiation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]