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: Surgery
Areas of carcinoma of oral mucosa can be identified by staining with - 
Select and explain. 
A. 1 % zinc chloride, B. 2 % silver nitrate, C. Gentian violet, D. 2 % toluidine blue
D: 2 % toluidine blue
Answer: D: 2 % toluidine blue 
Explanation: Helps to delineate the extent.