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 film is used for caries detection? (or) Which film
is used for caries detection in children? 
Select and explain. 
A. D speed, B. E speed, C. B speed, D. F speed
D: F speed
Answer: D: F speed 
Explanation: None