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': 'FG, FFG, FFFG is used to indicate: \nSelect and explain. \nA. Caridge, B. Black powder size, C. Base of gun, D. Wadding of caridge', 'role': 'user'}, {'content': "Answer: B \nExplanation: Black Gun Powder: Described as FG, FFG, FFFG, FFFFG depending on the fineness of the grain. The finer grains have more number of 'F'", 'role': 'assistant'}]