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
Which of the following is not affected by saliva? 
Select and explain. 
A. Impression plaster, B. Impression paste, C. Silicon impression material, D. None of the above
D: None of the above
Answer: D: None of the above 
Explanation: None