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
Most commonly used retarder in gypsum: 
Select and explain. 
A. Na2 SO4, B. Nacl, C. Citrates, D. K2 SO4
C: Citrates
Answer: C: Citrates 
Explanation: None