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': 'What is the major difference between a class V cavity preparation for amalgam and one for composite resin by the acid-etch technique? \nSelect and explain. \nA. Depth, B. Convenience form, C. Position of retentive points, D. Angulation of enamel cavosurface margins', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]