This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
[{'content': 'Which of the following has the maximum ionization potential \nSelect and explain. \nA. Electron, B. Helium ion, C. Proton, D. Gamma photon', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (Ref: Farr&;s physics for medical imaging 2e,23 )', 'role': 'assistant'}]