<prompt> Maximum oxygen concentration can be delivered by?  <response>: Choice D: Reservoir face mask is a high flow, variable performance device. At flow rate of 12-15Lmin 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. 