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': 'Three-wall defects most frequently occur: \nSelect and explain. \nA. On the lingual aspect, B. On the facial aspect, C. In the furcation, D. In the interdental area', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]