This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts, Subject name: Pathology
[{'content': 'Which of the following is the most common fixative used in electron microscopy? \nSelect and explain. \nA. Glutaraldehyde, B. Formalin, C. Picric acid, D. Absolute alcohol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Commonest fixative used for light microscopic examination: 10% buffered neutral formalin. Commonest fixative used for electron microscopic examination: Glutaraldehyde.', 'role': 'assistant'}]