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': 'All of the following are reasons for cone cut except: \nSelect and explain. \nA. Cone of radiation not covering the area of interest, B. PID not properly aligned with periapical film holder, C. Top of the film not immersed in the developing solution, D. Not enough film showing below or above the crowns of the teeth', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Cone cut:\n\nCause: Cone of radiation not covering the area of interest, not using film holders. Correction: Make sure that the cone is properly centered over the area of interest and the film, both vertically and horizontally.\nCause: PID\xa0not properly aligned with the periapical film holder. Correction: Position the PID carefully. If a film holder with an aiming ring is used, make sure that the PID and the aiming ring are aligned.\nCause: Top of the film not immersed in the developing solution.\xa0Correction: Maintain the level of the solution in the processing tanks and make sure that the film is completely immersed during processing.', 'role': 'assistant'}]