This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Stain for detecting early cancer in the oral and pharyngeal cavity is 
Select and explain. 
A. Silver nitrate, B. Toluidine blue, C. Congo red, D. Zinc chloride
B: Toluidine blue
Answer: B: Toluidine blue 
Explanation: .