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
Most widely used spring-loaded surveyor is: 
Select and explain. 
A. Ney surveyor, B. Jelenko surveyor, C. WillIams surveyor, D. None of the above
B: Jelenko surveyor
Answer: B: Jelenko surveyor 
Explanation: The most widely used surveyors are the Ney and the Jelenko.
Both of these are precision made instruments.
They differ principally in that the Jelenko arm swivels, whereas the Ney arm is fixed.