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
Impression plaster is: 
Select and explain. 
A. Less compressive than alginate, B. More compressive than alginate, C. As compressive as alginate, D. More compressive than hydrocolloids
A: Less compressive than alginate
Answer: A: Less compressive than alginate 
Explanation: IMPRESSION PLASTER
Impression plaster is a β-calcium sulfate hemihydrate used at a water/powder ratio of approximately 0.5 to 0.6. Its fluidity makes it suitable for making impressions of soft tissues in the uncompressed state, a characteristic of mucostatic impression material. 
Key concept: 
Impression plaster is less compressive than Alginate.
Ref: Phillips 12 ed page no 177