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': 'The American dental association (ADA) specification number for non- aqueous elastomeric dental impression material is: \nSelect and explain. \nA. 19, B. 20, C. 21, D. 26', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]