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': 'Which of the following impart structural durability in a three quarter crown  preparation on a mandibular molar? \nSelect and explain. \nA. Occlusal shoulder, B. Functional cusp bevel, C. Proximal groove, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]