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': 'The wall absent in class V lesion \nSelect and explain. \nA. Axial wall, B. Mesial, C. Distal, D. Pulpal wall', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]