<prompt> The optical density of gross fog is:0.6-3.00.2-0.30.2-0.6None of the above  <response>: 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 Pharoahs Oral Radiology Principles and Interpretation 8th edition 