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 impression tray are used for: \nSelect and explain. \nA. Alginate, B. Zinc oxide- eugenol, C. Agar-agar, D. Impression compound', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]