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
Multi axis grinding process is used in 
Select and explain. 
A. Hedstroem files, B. K files, C. K reamers, D. All of the above
A: Hedstroem files
Answer: A: Hedstroem files 
Explanation: None