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 function of proximal grooves in a class II cavity is: 
Select and explain. 
A. Resistance form, B. Retention form, C. Increases strength, D. Resistance and retention form
D: Resistance and retention form
Answer: D: Resistance and retention form 
Explanation: Secondary retention and resistance form

Retention grooves and locks are placed in the proximal box