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 zinc polycarboxylate modified setting time and 
increased manipulative properties are due to 
Select and explain. 
A. Bismuth Oxide, B. Stannic Oxide, C. Magnesium Oxide, D. Stannous Oxide
D: Stannous Oxide
Answer: D: Stannous Oxide 
Explanation: None