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: Pharmacology
[{'content': 'Which of the following gas exert second gas effect when co-administered with halothane? \nSelect and explain. \nA. Nitrous oxide, B. Chloroform, C. Ether, D. Helium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Second gas effect, diffusion hypoxia are seen with inhalation agents used in high concentration like nitrous oxide.', 'role': 'assistant'}]