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': 'Impression material that do not harden by chemical reaction: \nSelect and explain. \nA. Zinc oxide eugenol, B. Impression compound, C. Alginate, D. Plaster of paris', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Reversible materials, such as agar and impression compound, soften upon heating and solidify\xa0slightly\xa0above\xa0body\xa0temperature\xa0with\xa0no\xa0chemical change taking place.', 'role': 'assistant'}]