This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breathing Systems, Subject name: Anaesthesia
What is the pressure at which oxygen is stored? 
Select and explain. 
A. 75psi, B. 1600psi, C. 760 psi, D. 2200 psi
D: 2200 psi
Answer: D: 2200 psi 
Explanation: Ans. is 'd' i.e., 2200 psi GasType of cylinder and storage formColour codeCapacityPressurePin-IndexOxygenE. cylinderH. cylinder}GasBlack with white shoulderE-660 lit.H-6900 lit.2200 psi2.5Nitrous oxideEH}LiquidBlueE- 1590 lit.H-15800 lit.760 psi3.5AirE. gasGrey body with black & white shoulder625 lit.2000 psi1,5CarbondioxideE. liquidGrey-1590 lit750 psi2, 6 (< 7.5%)l, 6 (> 7.5%)CyclopropaneLiquidOrange-75 psi3.6HeliumGasBrown-1600 psi Entonox(50% O2 + 50% N.O2)LiquidBlud body with blue & white shoulder-2000 psiCentral (7)NitrogenGasGrey body with black shoulder---