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
All are feature of radiaiton except 
Select and explain. 
A. Biological, B. Photographic, C. Fluorescent, D. Non penetrating
D: Non penetrating
Answer: D: Non penetrating 
Explanation: D i.e. Non penetrating There is nothing to explain as radiation may be penetrating also. (Example gamma rays)