This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic Equipments, Subject name: Anaesthesia
As per ISO, color of NO2 cylinder is? 
Select and explain. 
A. Blue, B. Black, C. White, D. Red
A: Blue
Answer: A: Blue 
Explanation: Ans. A. Blue. (Ref. Lee anaesthesia 12th/pg. 104)COLOR AND PRESSURE OF CYLINDERS CylinderCOLORPRESSURE (BAR)1CyclopropaneOrange52NOBlue543 Grey504HalothaneAmber (Red)-5EthyleneRed-6HeliumBrown1377deg2Black body with white shoulder1378Entonox (50%O2+50%N2O)Blue with white shoulder1379ThiopentoneYellow-10N2Black-11AirGrey with white shoulder137