This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Histo Pathology, Subject name: Pathology
[{'content': 'All of the following stains are used for fat except? \nSelect and explain. \nA. Oil red O, B. Congo reds, C. Sudan black, D. Osmium tetroxide', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Congo red * Congo red is not used in lipid staining. It is used in the staining of amyloid protein.* Stain used for lipids (fatty acids)are Oil red O, Osmium tetroxide, sudan black and sudan III & IV.", 'role': 'assistant'}]