<prompt> All of the following factors are considered as safety measures in X-ray production except:Use of low kVp is recommendedUse of lead foil is mandatoryUse of high kVp is recommendedNone of the above  <response>: 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.White and Pharoahs Oral Radiology Principles and Interpretation 8th edition 