Explanation

Among the options, chlorofluorocarbons (CFCs) have the maximum average residence time in the atmosphere: they are extremely stable compounds that persist for many decades to centuries (some CFC types for well over a century), because they are destroyed only very slowly by ultraviolet radiation in the stratosphere. Methane lasts about 12 years, nitrous oxide about 114 years, and water vapour only days to weeks. The answer is (A).