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': '"Calibre" of fire arm is: \nSelect and explain. \nA. Distance between land and groove, B. Distance between two lands, C. Distance between two grooves, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Distance between two lands', 'role': 'assistant'}]