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': 'Perforated trays are used with \nSelect and explain. \nA. Alginate impression material, B. Silicone impression material, C. Modeling compound, D. Impression waxes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Perforated trays are used for alginate impression material to mechanically hold the impression in tray with the help of perforations.', 'role': 'assistant'}]