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: Anaesthesia
[{'content': 'Colour of Entonox cylinder is \nSelect and explain. \nA. Black body, white shoulder, B. Grey body, black and white shoulder, C. Black body, brown and white shoulder, D. Blue body, white shoulder', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Entonox cylinder has blue body and white shoulder.', 'role': 'assistant'}]