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: Unknown
[{'content': 'During staining for Electron Microscopy, the method which improves contrast of specimen is \nSelect and explain. \nA. Positive staining, B. Negative staining, C. Shadow staining, D. None of these', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The specimen stained with phosphotungstic acid in electron microscope for better visualisation of the structures. Negative staining with phosphotungstic acid used in electron microscope.', 'role': 'assistant'}]