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
[{'content': 'In firearm injury, entry-wound blackening is due to - \nSelect and explain. \nA. Flame, B. Hot gases, C. Smoke, D. Unburned powder', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]