This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Local and Regional Anesthesia, Subject name: Anaesthesia
[{'content': 'Oxygen cylinder color: \nSelect and explain. \nA. Black body white shoulder, B. White body black shoulder, C. Brown body and shoulder, D. Blue body and shoulder', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans: (a) Black body white shoulderRef: Miller's Anaesthesia 7th ed. / 675GasColor CodePin index positionBodyShoulderOxygenBlackWhite2,5Nitrous oxideBlueBlue3, 5CO2GrayGray1,6HeliumBrownBrown2,5AirGreyWhite/black quartered1,5", 'role': 'assistant'}]