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 N20 cylinder is 
Select and explain. 
A. Blue, B. Black, C. White, D. Red
A: Blue
Answer: A: Blue 
Explanation: To differentiate color coding is given to the cylinders . Blue - N20 Black - N2 Orange - Cyclopropane Grey - Co2 Black body with white shoulder - O2 Black body with brown shoulder - Heliox ( Helium + 02 )