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': 'Ramping can be done for a \nSelect and explain. \nA. one wall defect, B. two wall defect, C. three wall defect, D. four wall defect', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]