This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamental concepts, Subject name: Anaesthesia
Colour code of oxygen cylinder is 
Select and explain. 
A. Black cylinder with white shoulders, B. Black cylinder with grey shoulders, C. White cylinder with black shoulders, D. Grey cylinder with white shoulders
A: Black cylinder with white shoulders
Answer: A: Black cylinder with white shoulders 
Explanation: Color coding of cylinders is introduced to prevent accidental misplacement of cylinders.