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 asbestos liner is used in a casting ring to \nSelect and explain. \nA. Permit expansion of the mold, B. Retard heating of the investment, C. Facilitate venting of the mold, D. Both 1 and 3', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]