This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
[{'content': 'Diffusion hypoxia is seen with which drug: \nSelect and explain. \nA. Nitrous oxide, B. Ketamine, C. Theophylline, D. Halothane', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Nitrous oxideDiffusion hypoxia is side effect seen with nitrous oxide. It is seen when suddenly N2 O is stopped while recovering from anaesthesia. It can be prevented by supplying 100 percent O2 to the patient.', 'role': 'assistant'}]