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. 5 MV photons, C. 18MV photons, D. Proton beam', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Gamma rays (high energy photons) have the highest penetrating power. Therefore, 18 MeV photons will have high penetrating power.', 'role': 'assistant'}]