This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
At the end of anaesthesia after discontinuation of nitrous oxide and removal of endotracheal tube, 100% oxygen is administered to the patient to prevent – 
Select and explain. 
A. Diffusion Hypoxia, B. Second gas effect, C. Hyperoxia, D. Bronchospasm
A: Diffusion Hypoxia
Answer: A: Diffusion Hypoxia 
Explanation: Diffusion hypoxia can be prevented by continuing 100% O2 inhalation for a few minutes after discontinuing N2O, instead of straight away switching over to air.