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
True about mounting stones is 
Select and explain. 
A. Fast setting, B. High expansion, C. High strength, D. All of the above
A: Fast setting
Answer: A: Fast setting 
Explanation: The use of an articulator makes it necessary to mount the casts using a gypsum-producing product. These materials are referred to as "mounting" stones or plasters. They are fast setting and have low setting expansion. The mounting plaster has a sufficiently low strength to permit easy trimming and facilitate separating the cast from the articulator mounting plates.
Phillips Science of Dental Materials ed 12 pg 191