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
Extra retention in abutment teeth is obtained with: 
Select and explain. 
A. Dovetail, B. Slots, pins and grooves, C. Outline form, D. Increasing tooth reduction
B: Slots, pins and grooves
Answer: B: Slots, pins and grooves 
Explanation: None