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
The objectives of tooth preparation are all except: 
Select and explain. 
A. To conserve as much healthy tooth structure as possible, B. To remove all defects while providing protection  of  the  pulp–dentin  complex, C. To retain the defective, injured, or diseased  tooth form, D. To allow for the esthetic placement of a restorative material where indicated
C: To retain the defective, injured, or diseased  tooth form
Answer: C: To retain the defective, injured, or diseased  tooth form 
Explanation: Tooth preparation is the mechanical alteration of a defective, injured, or diseased tooth such that placement of restorative material reestablishes normal form (and therefore function) including esthetic corrections, where indicated.
Generally, the objectives of tooth preparation are to

Conserve as much healthy tooth structure as possible.
Remove all defects while simultaneously providing protection  of  the  pulp–dentin  complex.
Form  the  tooth preparation so that, under the forces of mastication, the tooth or the restoration (or both) will not fracture and the restoration will not be displaced, and
Allow for the esthetic placement of a restorative material where indicated.

Reference:  Sturdevant operative dentistry. 7th EDITION, Page No:120