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': 'Saftey H file is \nSelect and explain. \nA. Used in curved canals, B. Used in narrow canals, C. Used in bifurcated canals, D. Used in wide canals', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]