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
About 20 gms of hairs required to be preserved in 
Select and explain. 
A. Heavy metal poisoning, B. Aconite poisoning, C. Iodine poisoning, D. Codeine poisoning
A: Heavy metal poisoning
Answer: A: Heavy metal poisoning 
Explanation: Hair and nails are preserved in heavy metal poisoning e.g. arsenic, antimony, radium, thalium.