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': 'It is true about formalin - \nSelect and explain. \nA. That it can be used as preservative in alcohol poisoning, B. Never used as a preservative for chemical analysis, C. Used as a preservative in poisoning with digitalis, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Formaldehyde (formalin) is not used in poisoning because extraction of poisons especially non-volatile organic compounds become difficult in chemical analysis.', 'role': 'assistant'}]