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': 'The target of the X-ray tube is angulated to produce all the following effects, EXCEPT \nSelect and explain. \nA. To decrease the effective focal spot, B. To increase the image sharpness, C. To energize the photons, D. To dissipate heat', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The target is inclined about 20 degrees to the central ray of the x-ray beam; this causes the effective focal spot to be approximately 1 mm × 1 mm, as opposed to the actual focal spot, which is about 1 mm × 3 mm.\xa0\nThis smaller effective focal spot results in a small apparent source of x rays and an increase in the sharpness of the image, with a larger actual focal spot size to improve heat dissipation.\nRef: Oral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 6', 'role': 'assistant'}]