This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
[{'content': 'Stain used in electron microscopy? \nSelect and explain. \nA. 2.5% glutaldehyde, B. Phosphotungstic acid, C. Saffranin, D. Coomassie blue', 'role': 'user'}, {'content': "Answer: B \nExplanation: Electron microscope: the technique of shadow casting with vapourised heavy metals has made pictures with good contrast and 3D effect possible. Another valuable technique in studying fine structure is negative staining with phosphotungstic acid REF:Ananthanarayan & Panicker's Textbook of Microbiology 8th Edition pg no: 13", 'role': 'assistant'}]