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': 'Value of total filtration for 70 kVp is \nSelect and explain. \nA. 2.1 mm, B. 2.3 mm, C. 1.5 mm, D. 2.5 mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Total\xa0filtration\xa0is\xa0the\xa0sum\xa0of\xa0the\xa0inherent\xa0and\xa0added 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\xa0of\xa0aluminum\xa0for\xa0machines\xa0operating\xa0at\xa0higher\xa0voltages.\nOral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 10,11', 'role': 'assistant'}]