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 special tray which is used for agar impression material, has a water channel, which helps in setting of the material. The temperature of water flowing in channel is 
Select and explain. 
A. 25 deg - 35 deg, B. 37 deg - 45 deg, C. 15 deg - 17 deg, D. 18 deg - 21 deg
D: 18 deg - 21 deg
Answer: D: 18 deg - 21 deg 
Explanation: None