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 which has a high incidence of air porosity is \nSelect and explain. \nA. Alginate impression material, B. Impression compound, C. Zinc oxide eugenol impression paste, D. Polyether impression material', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]