This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitreous and retina, Subject name: Ophthalmology
[{'content': 'In retinal sealing/retinopexy, what is used? \nSelect and explain. \nA. Sulphur hexafluoride, B. Carbon monooxide, C. Nitrous oxide, D. S02', 'role': 'user'}, {'content': "Answer: A \nExplanation: The gases commonly employed for tamponading the retina are sulphur hexafluoride (SF6) or perfluoropropane (C3F8). These are injected after sealing the breaks with cryopaxy. The gas bubble remains in contact with the tear for 5-7 days and are absorbed later. Ref: Parson's 22 nd edition page no. 335", 'role': 'assistant'}]