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 is not a feature of biologic requirement of tooth preparation \nSelect and explain. \nA. Conservation of tooth structure, B. Avoidance of overcontouring, C. Subgingival margins, D. Harmonious occlusion', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]