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: Surgery
You want assistant to get entonox gas cylinder ,which color will you order him to get? 
Select and explain. 
A. Black body white shoulder, B. Blue body white shoulder, C. White body black shoulder, D. White body blue shoulder
B: Blue body white shoulder
Answer: B: Blue body white shoulder 
Explanation: Entonox has blue body with white shoulder color code for cylinder