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
[{'content': 'Techniques for preparing narrow and curved canals: \nSelect and explain. \nA. Step down technique, B. Modified double flare technique, C. Balanced force technique, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Techniques for preparing narrow and curved canals are:\n\nStep down\nModified double flare\nBalanced force technique', 'role': 'assistant'}]