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 the most penetration beam? \nSelect and explain. \nA. Electron beam, B. 8 MV photons, C. 18 MV photons, D. Proton beam', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The order of penetration power is ? rays> electrons> a paicles. Here the 18MeV photon will have more energy than 8MeV photon. Ref: Essentials of Environmental Health, By Robe H. Friis, 2011, Page 191', 'role': 'assistant'}]