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
If exposure of film A is R then Exposure of film E is : 
Select and explain. 
A. 1/2 R, B. 1/4 R, C. 1/8 R, D. 1/16 R
D: 1/16 R
Answer: D: 1/16 R 
Explanation: None