This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Flow Volume curve, Spirometry and DLCO, Subject name: Medicine
Maximum oxygen concentration can be delivered by? 
Select and explain. 
A. <img style="max-width: 100%" src=" />, B. <img style="max-width: 100%" src=" />, C. <img style="max-width: 100%" src=" />, D. <img style="max-width: 100%" src=" />
D: <img style="max-width: 100%" src=" />
Answer: D: <img style="max-width: 100%" src=" /> 
Explanation: Choice D: Reservoir face mask is a high flow, variable performance device. At flow rate of 12-15L/min the delivered Fi02 is in the range of 75-90%. Choice C is simple face mask while choice B is Nasal cannula and both can deliver limited oxygen up to 40% due to diffusion and mixing with air. Choice A: Venturi mask is a high flow, fixed performance device. It can deliver up to 60% oxygen.