This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Medicine
Colour coding for Nitrous oxide cylinder is 
Select and explain. 
A. Black, B. Black with white shoulders, C. French blue, D. Gray
C: French blue
Answer: C: French blue 
Explanation: (C) French blue IDENTIFICATION OF MEDICAL GAS CYLINDERSGasColor of cylinderPressure at 15degC when full British standard (Body/Shoulder)United StatesLbf/in2Bar1. Oxygen (O2)Black / WhiteGreen19871372. Nitrous oxide (N2O)French blueBlue638443. CyclopropaneOrangeOrange7354. Carbondioxide (CO2)GreyGrey725505. Helium (He)BrownBrown19871376. AirGreyYellow19871377. O^HeliumBlackGreen/Brown19871378. OJC02BlackGreen/Grey19871379. EntonoxBlueBlue/Green1987137