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
Heel-raising movement of a RPD is prevented by: 
Select and explain. 
A. Occlusal rests, B. Minor connector, C. Direct retainer, D. Indirect retainer
D: Indirect retainer
Answer: D: Indirect retainer 
Explanation: None