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
In a class III cavity in an incisor tooth the retentive points are placed: 
Select and explain. 
A. At the expense of facial and Lingual walls and not in dentin, B. Entirely in dentin, C. In axial wall, D. By placing a groove in the lingual surfaces
B: Entirely in dentin
Answer: B: Entirely in dentin 
Explanation: None