This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Death and Investigations, Subject name: Forensic Medicine
[{'content': 'Calibre is defined as: \nSelect and explain. \nA. Distance between two diametrically opposite lands, B. Distance between two diametrically opposite grooves, C. Distance between opposite land and groove, D. Ratio of the length and width of the barrel', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. a. Distance between two diametrically opposite lands (Ref: Parikh's 6/e p4.26; Reddy 33/e p210)Calibre is defined as distance between two diametrically opposite lands.'The calibre of a rifled firearm is measured between a pair of diametrically opposite 'lands' across the bore. Textbook Of Forensic Medicine And Toxicology: Principles And Practice By Vij (2008)/309Some Important Terms Related to FirearmsCalibreDistance between two diametrically opposite /andsQActionAction means the assembly of the firing mechanism of the gunQ.BallisticsScience of the motion of a projectile", 'role': 'assistant'}]