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: Medicine
[{'content': 'Which of the following is used for preservation of alcohol? \nSelect and explain. \nA. Potassium acetate, B. Sodium sulphide, C. Sodium fluoride, D. Glycerine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (Sodium fluoride)\n\nSodium fluoride is a useful preservative in a suspected case of alcohol poisoning.\nIt is done with mixing 10 mL of blood with potassium oxalate & sodium fluoride (enzyme inhibitors)\nfor suspected alcohol poisoning.\nA preservative (sodium fluoride, 0.5 -2% weight by volume) should be added after collecting a vitreous humour sample for ethanol analysis in postmortem toxicology cases.\nGastric contents can be stored in saturated salt solution.', 'role': 'assistant'}]