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': 'All of the following factors are considered as safety measures in X-ray production except: \nSelect and explain. \nA. Use of low kVp is recommended, B. Use of lead foil is mandatory, C. Use of high kVp is recommended, D. None of the above', 'role': 'user'}, {'content': "Answer: A \nExplanation: The optimal operating potential of dental X-ray units is between 60 and 70 kVp (ADA 2012). Although image diagnosis may be improved slightly with increased image contrast (low kVp) images, the patient dose is reduced with higher kVp exposures.\nWhite and Pharoah's Oral\xa0 Radiology Principles and Interpretation 8th edition", 'role': 'assistant'}]