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
All of the following device work on traction principle except: 
Select and explain. 
A. Ferrier double bow separator., B. Elliot separator., C. Perry separator., D. None
B: Elliot separator.
Answer: B: Elliot separator. 
Explanation: Elliot separator work on wedge principle.