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 has most penetrating power? 
Select and explain. 
A. a paicle, B. b paicle, C. g - radiation, D. Electron beam
C: g - radiation
Answer: C: g - radiation 
Explanation: Penetration power maximum for gamma rays (1000 times of a rays). Minimum for alpha rays. Ref: Park's Preventive and Community Medicine, 16th Edition, Page 514 and 17th Edition, Page 521