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': 'In K-file the most common type of motion is \nSelect and explain. \nA. Watch winding, B. Linear, C. Rotating through 90° arch, D. Linear & clockwise', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]