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
Threaded pins are used in large dental amalgam restorations to provide: 
Select and explain. 
A. Retention form, B. Resistance form, C. Occlusal stops for opposing teeth, D. Much needed reinforcement of the amalgam
A: Retention form
Answer: A: Retention form 
Explanation: None