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: Pathology
[{'content': "Which of the following is the most commonly used 'fixative' in diagnostic pathology? \nSelect and explain. \nA. Formaldehyde, B. Ethyl alcohol, C. Mercuric chloride, D. Picric acid", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Formaldehyde is the most commonly used fixative in diagnostic pathology. Ref: Surgical Pathology Dissection: An Illustrated Guide By William H. Westra, Page 14.', 'role': 'assistant'}]