"In the whole scheme of things, green roofs are not the one answer to sequestering carbon, but they will certainly help."Green roofs offer a long list of known benefits. They lower air-conditioning costs in the summer by absorbing and reflecting heat. They lower heating costs in the winter by adding extra isolation.Green roofs appeal to cities because they soak up rainwater, making excess storm-water less likely to flood sewage (下水道) systems and increase sewage treatment costs. Plant-filled roofs make urban areas less likely to become heat islands. They reduce air pollution and noise pollution. And plants, even when it's several stories up, provides living places for animals.A green roof's ability to sequester carbon lasts only a year or two. At that point, the amount of carbon emitted by the decay of soil and plant material balances out the carbon taken in by photosynthesis (光合作用). Still, that's two extra years of balance that a green roof potentially provides.What does the word "sequester" mean in the sentence "In the whole scheme of things, green roofs are not the one answer to sequestering carbon...?" (Para. 3)

While green roofs certainly won't solve the global warming problem, their ability to absorb greenhouse gases—even just a little bit—supports the case for planting them on city buildings, despite extra costs on the front end, said lead researcher Kristin Getter, of Michigan State University in East Lansing. "The key to fighting global warming is capturing carbon from the atmosphere and storing it in new reservoirs that weren't storing carbon before," Getter said. "In the whole scheme of things, green roofs are not the one answer to sequestering carbon, but they will certainly help." Green roofs offer a long list of known benefits. They lower air-conditioning costs in the summer by absorbing and reflecting heat. They lower heating costs in the winter by adding extra isolation. Green roofs appeal to cities because they soak up rainwater, making excess storm-water less likely to flood sewage (下水道) systems and increase sewage treatment costs. Plant-filled roofs make urban areas less likely to become heat islands. They reduce air pollution and noise pollution. And plants, even when it's several stories up, provides living places for animals. A green roof's ability to sequester carbon lasts only a year or two. At that point, the amount of carbon emitted by the decay of soil and plant material balances out the carbon taken in by photosynthesis (光合作用). Still, that's two extra years of balance that a green roof potentially provides. What does the word "sequester" mean in the sentence "In the whole scheme of things, green roofs are not the one answer to sequestering carbon...?" (Para. 3) A. Decay. B. Recirculate. C. Remove. D. Decompose.