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': 'A cross-section of the cervical third of the pulp canal of a maxillary second premolar resembles in shape: \nSelect and explain. \nA. A circle, B. A square, C. A triangle, D. An ellipse', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]