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
Gypsum product having least expansion: 
Select and explain. 
A. Impression plaster, B. Model plaster, C. Stone plaster, D. Die stone
D: Die stone
Answer: D: Die stone 
Explanation: DENTAL STONE, HIGH STRENGTH (TYPE IV)
The principal requisites for a die material are strength, hardness, and minimal setting expansion. To obtain these properties, modified α-hemihydrate is used. The cube-shaped particles and the reduced surface area produce such properties without undue thickening of the mix. This material is also called die stone.