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 pins in an amalgam restorative serve to: 
Select and explain. 
A. Increase strength, B. Increase retention, C. Increase resistance of fracture, D. All the above
B: Increase retention
Answer: B: Increase retention 
Explanation: None