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': 'About 20 gms of hairs required to be preserved in \nSelect and explain. \nA. Heavy metal poisoning, B. Aconite poisoning, C. Iodine poisoning, D. Codeine poisoning', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hair and nails are preserved in heavy metal poisoning e.g. arsenic, antimony, radium, thalium.', 'role': 'assistant'}]