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: Microbiology
[{'content': 'Stain for premalignant lesions \nSelect and explain. \nA. Toluidine blue, B. Malachite green, C. Potassium iodide, D. Iodine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Toluidine blue is the stain for premalignant lesions.', 'role': 'assistant'}]