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
Trisodium phosphate in alginate acts as: 
Select and explain. 
A. Retarder, B. Reactor, C. Accelerator, D. Plasticizer
A: Retarder
Answer: A: Retarder 
Explanation: None