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
[{'content': 'In which of the following materials, moisture loss has to be taken care of? \nSelect and explain. \nA. Alginate impression, B. Polyvinyl siloxane, C. Both, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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.\nPreoperative PVS impressions do not need to be wrapped. The preoperative impression is placed aside for later use in forming the temporary restoration.\n\nSturdevant operative dentistry\xa07th Edition, Page No:120', 'role': 'assistant'}]