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 the following are features of radiation except: 
Select and explain. 
A. Fluorescein, B. Biological, C. Photographic, D. Non penetrating
D: Non penetrating
Answer: D: Non penetrating 
Explanation: Ans. Non penetrating