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
[{'content': 'If exposure of film A is R then Exposure of film E is : \nSelect and explain. \nA. 1/2 R, B. 1/4 R, C. 1/8 R, D. 1/16 R', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]