This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia, Subject name: Pharmacology
[{'content': 'Colour of oxygen cylinder is \nSelect and explain. \nA. Black body with white shoulder, B. Black body with grey shoulder, C. Grey body with white shoulder, D. Grey body with black shoulder', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Refer anesthetic equipments and procedures, Practical Approach /p 37,38. The color of a medical oxygen xylinder6 is a black body with a white shoulder', 'role': 'assistant'}]