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': 'H type endodontic instrument has a spiral edge arranged to allow cutting during \nSelect and explain. \nA. Pushing stroke, B. Pulling stroke, C. Circular stroke, D. Oblong stroke', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]