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': 'FC FFG, FFFG ... used to describe- \nSelect and explain. \nA. Primer, B. Cartridge, C. Black gunpowder, D. Base of firearms', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Depending on fineness, the black gun powder is designated as FG, FFG, FFFG etc (F = fineness).', 'role': 'assistant'}]