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
Master cone is 
Select and explain. 
A. First instrument using taking working length, B. Used by master of staff, C. Fully snug fit with accurate working length, D. Last fill to fit loosely
C: Fully snug fit with accurate working length
Answer: C: Fully snug fit with accurate working length 
Explanation: None