This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mechanical injuries, Subject name: Forensic Medicine
Di collar or grease collar is seen in - 
Select and explain. 
A. Punctured wound by sharp weapon, B. Lacerated wound, C. Firearm entry wound, D. Stab wound
C: Firearm entry wound
Answer: C: Firearm entry wound 
Explanation: The synopsis of forensic medicine & toxicology ; Dr k.s narayan reddy ; 28th edition ;pg.no 131 A di collar is seen in firearm entry wound ,it is seen as narrow ring of skin ,lining the defect & is sharply outlined . This results from the removal of substances from the bullet as it passes through the skin ,i.e bullet lubrication ,gun oil from the interior of the barrel ,lead from the surface of bullet ,barrel debris etc .