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': 'Definition and Detail Describes: \nSelect and explain. \nA. Image sharpness., B. Increases as focal spot size reduce, C. Reduces as focal spot size increases., D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]