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
In which of the following materials, moisture loss has to be taken care of? 
Select and explain. 
A. Alginate impression, B. Polyvinyl siloxane, C. Both, D. None
A: Alginate impression
Answer: A: Alginate impression 
Explanation: Alginate impressions can distort quickly if they are allowed to gain or lose moisture, so the impression is wrapped in wet paper towels to serve as a humidor.
Preoperative PVS impressions do not need to be wrapped. The preoperative impression is placed aside for later use in forming the temporary restoration.

Sturdevant operative dentistry 7th Edition, Page No:120