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
Extension for prevention is directly related to: 
Select and explain. 
A. 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
D: The outline form of the cavity preparation
Answer: D: The outline form of the cavity preparation 
Explanation: None