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
Techniques for preparing narrow and curved canals: 
Select and explain. 
A. Step down technique, B. Modified double flare technique, C. Balanced force technique, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Techniques for preparing narrow and curved canals are:

Step down
Modified double flare
Balanced force technique