This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oral cavity, Subject name: Surgery
[{'content': 'Areas of carcinoma of oral mucosa can be identified by staining with: \nSelect and explain. \nA. 1% zinc chloride, B. 2% silver nitrate, C. Gentian violet, D. 2% toluidine blue', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Toluidine Blue Toluidine blue is a basic metachromatic dye with high affinity for acidic tissue components, thereby staining tissues rich in DNA and RNAQ. Wide applications both as vital staining in living tissues and as a special stain used in vivo to identify dysplasia and carcinoma of the oral cavityQ.', 'role': 'assistant'}]