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 impression material with lowest viscosity is 
Select and explain. 
A. Plaster of paris, B. Agar-agar, C. Zinc oxide eugenol, D. Elastomers
A: Plaster of paris
Answer: A: Plaster of paris 
Explanation: 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.
Ref: Phillips 12 ed page no 177