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': 'Agar polymer has \nSelect and explain. \nA. Brush heap structure, B. Interdigitation structure, C. Fish belly structure, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Composition of Commercial Reversible Hydrocolloid Impression Materials:', 'role': 'assistant'}]