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
Which of the following is not a feature of biologic requirement of tooth preparation 
Select and explain. 
A. Conservation of tooth structure, B. Avoidance of overcontouring, C. Subgingival margins, D. Harmonious occlusion
C: Subgingival margins
Answer: C: Subgingival margins 
Explanation: None