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 one of the following has the maximum ionization potential? \nSelect and explain. \nA. Electron, B. Proton, C. Helium ion, D. Gamma – Photon', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Penetration power : Gamma rays> X rays > Beta particle >Alpha particle (or helium ion) Ionizing & damaging power: is reserve Alpha particle (or helium ion) > Beta particle > X ray> Gamma ray', 'role': 'assistant'}]