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
Calcified canal is explored with all of the given instruments except: 
Select and explain. 
A. 6 K file, B. C+ file, C. 10 K file, D. Profinder
C: 10 K file
Answer: C: 10 K file 
Explanation: Canal exploration: 8, 10 K file used. 
In calciﬁed canal exploration: 6 K ﬁle, C+ ﬁle, proﬁnder.