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': 'Extension for prevention is directly related to: \nSelect and explain. \nA. Removal of unsupported enamel on proximal surface of Class III cavity, B. Depth of the axial wall of a class III cavity preparation, C. Elimination of all carious dentin beyond average depth of pulpal wall, D. The outline form of the cavity preparation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]