This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ballistics, Subject name: Forensic Medicine
[{'content': 'Smokeless Gun powder contains \nSelect and explain. \nA. Nitrocellulose, B. Charcoal, C. Potassium, D. Sulphur', 'role': 'user'}, {'content': 'Answer: A \nExplanation: SMOKELESS gun powder: Single base: Nitrocellulose Double base: Nitrocellulose + Nitro-glycerine Triple base: Nitrocellulose + Nitroglycerine + Nitroguanidine', 'role': 'assistant'}]