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
Sol- gel transformation is seen in 
Select and explain. 
A. Impression plaster, B. Hydrocolloids, C. Elastomer, D. Impression compound
B: Hydrocolloids
Answer: B: Hydrocolloids 
Explanation: The typical sol-gel reaction can be described simply as a reaction of soluble alginate with calcium ions from calcium sulfate and the formation of an insoluble calcium alginate.
Ref:  Phillips 12edition page no 172