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
[{'content': 'Elastomers are \nSelect and explain. \nA. Alginate, B. Agar, C. Polyethers, D. Impression compound', 'role': 'user'}, {'content': 'Answer: C \nExplanation: According to Chemistry \nChemically, there are four kinds of elastomers:\n\nPolysulfide\nCondensation polymerizing silicones\nAddition polymerizing silicones\nPolyether', 'role': 'assistant'}]