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 inherent filtration of X-ray machines range from\n___________ thickness of aluminium \nSelect and explain. \nA. 0.5 - 2 mm, B. 1.5 - 2.5 mm, C. 2.5 - 5 mm, D. 1.0 - 2.5 mm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Inherent filtration consists of the materials that x-ray photons encounter as they travel from the focal spot on the target to form the usable beam outside the tube enclosure. These materials include the glass wall of the x-ray tube, the insulating oil that surrounds many dental tubes, and the barrier material that prevents the oil from escaping through the x-ray port. The inherent filtration of most x-ray machines ranges from the equivalent of 0.5 to 2 mm of aluminum.\nAdded filtration\xa0may be supplied in the form of aluminum disks placed over the port in the head of the x-ray machine.\xa0\nTotal\xa0filtration\xa0 is the sum of the inherent and added filtration. Governmental regulations require the total filtration in the path of a dental x-ray beam to be equal to the equivalent of 1.5 mm of aluminum for a machine operating at up to 70 kVp and 2.5 mm of aluminum for machines operating\xa0 at\xa0 higher voltages.\nOral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 10,11', 'role': 'assistant'}]