This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Special topics, Subject name: Forensic Medicine
Never used in chemical analysis 
Select and explain. 
A. Saturated NaCl solution, B. Formalin, C. Rectified spirit, D. Sodium fluoride
B: Formalin
Answer: B: Formalin 
Explanation: Formalin cannot be used for preservation because it hardens and fixes the tissues and poison cannot be extracted. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 404