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
Which one of the following has the maximum ionization potential? 
Select and explain. 
A. Electron, B. Proton, C. Helium ion, D. Gamma – Photon
C: Helium ion
Answer: C: Helium ion 
Explanation: 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