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: Ophthalmology
[{'content': 'Fluorescein dye is used to stain \nSelect and explain. \nA. Disease and devitalized cells, B. Areas of denuded epithelium, C. Mucus, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Fluorescein dye is used to stain areas of denuded epithelium.\nRose Bengal stains disease and devitalized cells.\nAlcian Blue stains the mucus.', 'role': 'assistant'}]