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
The cross linking agent of polysulphide rubber base impression material is 
Select and explain. 
A. Aromatic sulfonate esters, B. Stannous octate, C. Platinum salt catalyst, D. Lead dioxide
D: Lead dioxide
Answer: D: Lead dioxide 
Explanation: None