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: Dental
According to ADA Specification No. 28, what is the rate of increase in file diameter per running millimeter of length for a K-type file from point D0 to point D16? 
Select and explain. 
A. 0.02 mm per running millimeter of length, B. 0.04 mm per running millimeter of length, C. 0.06 mm per running millimeter of length, D. Parallel sided, so no increase in diameter
A: 0.02 mm per running millimeter of length
Answer: A: 0.02 mm per running millimeter of length 
Explanation: Each number should represent diameter of instrument in 100th of millimeter at the tip. 
For example, a No. 25 K file shall have 0.25 mm at D1 and 0.57 mm (0.25 + 0.32) at D2. 
These sizes ensure a constant increase in taper, i.e. 0.02 mm/mm of the instrument regardless of the size.