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': 'A 26 year old male presented to the dental clinic with pain in the right lower back tooth region. On examination, it was evident that pericoronitis is present with #48. The inherent filtration of the machine used is 3 mm of Aluminium operating at 70 kVp. By the use of this machine, the surface exposure: \nSelect and explain. \nA. Reduces to 20% of the exposure without filtration, B. Reduces to 80% of the exposure without filtration, C. Reduces to 30% of the exposure without filtration, D. Is not reduced at all', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Filtration results in decreased patient exposure with no loss of radiographic information.\n\xa0\nWhen an X-ray beam is filtered with 3 mm of aluminum, the surface exposure is reduced to approximately 20% of the exposure with no filtration.\n\xa0\nReference: ORAL RADIOLOGY PRINCIPLES AND INTERPRETATION,8th EDITION, Stuart C. White,Michael J. Pharoah', 'role': 'assistant'}]