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 of the following is the most penetration beam – 
Select and explain. 
A. Electron beam, B. 5 MV photons, C. 18MV photons, D. Proton beam
C: 18MV photons
Answer: C: 18MV photons 
Explanation: Gamma rays (high energy photons) have the highest penetrating power. Therefore, 18 MeV photons will have high penetrating power.