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
Perforated impression tray are used for: 
Select and explain. 
A. Alginate, B. Zinc oxide- eugenol, C. Agar-agar, D. Impression compound
A: Alginate
Answer: A: Alginate 
Explanation: None