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
The asbestos liner is used in a casting ring to 
Select and explain. 
A. Permit expansion of the mold, B. Retard heating of the investment, C. Facilitate venting of the mold, D. Both 1 and 3
A: Permit expansion of the mold
Answer: A: Permit expansion of the mold 
Explanation: None