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 operator should stand at a distance of _______ while\ntaking X-ray. \nSelect and explain. \nA. 6 feet, B. 8 feet, C. 10 feet, D. 2 meters', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Means for Reducing X-Ray Exposure:\xa0\n\nUse selection criteria to assist in determining type and frequency of radiographic examinations.\xa0\nUse E/F-speed film or digital sensors.\xa0\nUse holders to support film or digital sensors intraorally.\nMake exposures with 60 to 70 kVp.\xa0\nReplace short pointed aiming tubes with open-ended aiming cylinders.\xa0\nUse rectangular collimation for periapical and bitewing images.\xa0\nUse thyroid collars.\xa0\nStand at least 6 feet (2 m) away from patient and away from the X-ray machine (preferably out of X-ray room) when making exposure.\xa0\nWith film, use time-temperature film processing rather than "sight" processing, or use an automatic processor.\xa0\nUse rare-earth screens for panoramic and cephalometric film imaging or use digital systems.\xa0\nReduce cone-beam CT beam field of view to region of interest.\xa0\n\nReference: White and Pharoah\'s Oral Radiology Principles and Interpretation 7th edition page no 33', 'role': 'assistant'}]