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: Ophthalmology
[{'content': 'Pneumoretinopexy is an outpatient procedure in which retinal detachmentis sealed with air insufflation. Which of the follov gas is used in pneu-etitiopexy? \nSelect and explain. \nA. Sulfur hexafluoride, B. Carbon dioxide, C. Nitrous oxide, D. Oxygen', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. Sulfur hexafluoride', 'role': 'assistant'}]