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
Value of total filtration for 70 kVp is 
Select and explain. 
A. 2.1 mm, B. 2.3 mm, C. 1.5 mm, D. 2.5 mm
C: 1.5 mm
Answer: C: 1.5 mm 
Explanation: Total filtration is the sum of the inherent and added 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 of aluminum for machines operating at higher voltages.
Oral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 10,11