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': 'Intrabony defects are \nSelect and explain. \nA. one-walled defects, B. two-walled defects, C. three walled defects, D. combination of above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]