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
The size of periapical film used in adults is 
Select and explain. 
A. 21 x 31 mm, B. 31 x 41 mm, C. 22 x 35 mm, D. None of the above
B: 31 x 41 mm
Answer: B: 31 x 41 mm 
Explanation: None