This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Which of the following can deliver 90% oxygen? 
Select and explain. 
A. Venturi mask, B. Rebreathing O2 mask, C. Nasal prongs, D. Non-rebreathing mask with O2reservoir bag
B: Rebreathing O2 mask
Answer: B: Rebreathing O2 mask 
Explanation: Non rebreathing masks: Can deliver upto 80% of oxygen. Rebreathing mask: When tightly fit, they can provide 100%oxygen.(Refer: Morgan's Clinical Anaesthesiology, 4th edition, pg no: 38-40)