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 for the extension of the proximal margins are all except: 
Select and explain. 
A. Include all caries lesions, defects or existing restorative materials, B. Create 90-degree cavosurface margins, C. Establish not more than 0.5 mm clearance with the adjacent proximal surface facially, lingually and gingivally, D. The location of the final proximal margins should be established with No.245 bur
D: The location of the final proximal margins should be established with No.245 bur
Answer: D: The location of the final proximal margins should be established with No.245 bur 
Explanation: The objectives for the extension of the proximal margins are to:

Include all caries lesion, defects or existing restorative material.
Create approximately 90o cavosurface margins (i.e., butt-joint margins). 
Establish (ideally) not more than 0.5 mm clearance with the adjacent proximal surface facially, lingually, and gingivally.

The location of the final proximal margins (i.e., facial, lingual, gingival) should be established with hand instruments (i.e., chisels, hatchets, trimmers) and not the No.245 bur, so as to prevent unnecessary overextension.
Reference: Sturdevant operative dentistry. 7th EDITION,  Page No:341