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
Saftey H file is 
Select and explain. 
A. Used in curved canals, B. Used in narrow canals, C. Used in bifurcated canals, D. Used in wide canals
A: Used in curved canals
Answer: A: Used in curved canals 
Explanation: None