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 optical density of gross fog is: 
Select and explain. 
A. 0.6-3.0, B. 0.2-0.3, C. 0.2-0.6, D. None of the above
B: 0.2-0.3
Answer: B: 0.2-0.3 
Explanation: An unexposed film, when processed, shows some density. This appearance is caused by the inherent density of the base and added tint and the development of a few unexposed silver halide crystals. This minimal density is called base plus fog and typically is 0.2 to 0.3. 
 
White and Pharoah's Oral  Radiology Principles and Interpretation 8th edition