This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Death and postmortem changes, Subject name: Forensic Medicine
For biochemical analysis vitreous in sent in - 
Select and explain. 
A. Hydrochloric acid, B. Phenol, C. Formalin, D. Fluoride
D: Fluoride
Answer: D: Fluoride 
Explanation: 10 mg fluoride in every 1 ml of vitreous humor is added for preservation in analysis of alcohol, cocaine, cyanide and CO. Dr. Narayana Reddys Synopsis of Forensic Medicine & Toxicology 27 th edition pg. 62.