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
[{'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: Helps to delineate the extent.', 'role': 'assistant'}]