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
Conservation of tooth structure during biomechanical preparation of crown can be done by 
Select and explain. 
A. Use of partial-coverage restorations, B. Minimum practical convergence angle (taper) between axial walls, C. Preparation of the occlusal surface, so reduction follows the anatomic planes, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Tooth structure is conserved by using the following guidelines: 

Use of partial-coverage rather than completecoverage restorations.
Preparation of teeth with the minimum practical convergence angle (taper) between axial walls.
Preparation of the occlusal surface so reduction follows the anatomic planes to give uniform thickness in the restoration.
Preparation of the axial surfaces so tooth structure is removed evenly; if necessary, teeth should be orthodontically repositioned.
Selection of a conservative margin compatible with the other principles of tooth preparation.
Avoidance of unnecessary apical extension of the preparation.