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
Tattoing in entry wound of a firearm injury is due to? 
Select and explain. 
A. Burning, B. Smoke, C. Gun powder, D. Wads
C: Gun powder
Answer: C: Gun powder 
Explanation: Ans. is 'c' i.e., Gun powder