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: Forensic Medicine
[{'content': 'Brain is presented for study in - \nSelect and explain. \nA. 10% formalin, B. 20% formalin, C. 30% formalin, D. 40% formalin', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. 10% formalin 10% formalin is used as preservative for histopathological examination of tissue but not used for poisoning or chemical analysis.", 'role': 'assistant'}]