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 one of the following may NOT be used during the
flanking of dentures: 
Select and explain. 
A. petroleum, B. tin foil, C. tin foil substitute, D. silicone lubricant
A: petroleum
Answer: A: petroleum 
Explanation: None