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': 'Which of the following impression material is rigid? \nSelect and explain. \nA. Zinc oxide-eugenol, B. Reversible hydrocolloid, C. Alginate, D. Polysulphide rubber', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Key Concept:\xa0ZnO Eugenol impression paste is rigid (inelastic) impression material.', 'role': 'assistant'}]