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': 'All are components of gun-powder except - \nSelect and explain. \nA. Charcoal, B. Lead peroxide, C. Potassium nitrate, D. Sulphur', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]