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': 'Cross section of K-flex file is: (OR) K-flex file is traditionally made form \nSelect and explain. \nA. Rhomboidal, B. Circular, C. Spiral, D. Double helix', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]