This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Anatomy
[{'content': 'The barrel is scored internally with a number of shallow spiral grroves, called \nSelect and explain. \nA. Rifling, B. Choking, C. Blackening, D. Tattooing', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Rifles The barrel is scored internally with a number of shallow spiral grooves varying from 4-7 and most commonly 6. These grooves are called rifling. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 136', 'role': 'assistant'}]