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': 'Which of the following agent is used as a die hardener? \nSelect and explain. \nA. Cynoacrylate, B. Nail polish, C. Volatile relief agents, D. Composite Resin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]