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': 'Black gun powder made of -a) Potassium nitrateb) Charcoalc) Sulfur powderd) Cellulose nitratee) Barium sulfate \nSelect and explain. \nA. ab, B. abc, C. acd, D. bcd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The classical gun powder is known as black powder, consists of charcoal (15%), sulphur (10%), and potassium nitrate (75%).', 'role': 'assistant'}]