Cars account for half the oil consumed in the U. S. , about half the urban pollution and one fourth the greenhouse(温室)gases. The

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问题     Cars account for half the oil consumed in the U. S. , about half the urban pollution and one fourth the greenhouse(温室)gases. They take a similar toll(损耗)of resources in other industrial nations and in the cities of the developing world. As vehicle-use continues to increase in the coming decade, the U. S. and other countries will have to deal with these issues or else face unacceptable economic, health-related and political costs. It is unlikely that prices will remain at their current low level or that other nations will accept a large and growing U. S. contribution to global climatic change.
    Policymakers and industry have four options: reduce vehicle use, increase the efficiency and reduce the emissions of conventional gasoline-powered vehicles, switch to less harmful fuels, or find less polluting driving systems. The last of these—in particular the introduction of vehicles powered by electricity—is ultimately the only sustainable option. The other alternatives are attractive in theory but in practice are either impractical or offer only marginal improvements. For example, reduced vehicle use could solve traffic problems and a host of social and environmental problems, but evidence from around the world suggests that it is very difficult to make people give up their cars to any significant extent. In the U.S. , mass-transit ridership and carpooling(合伙用车)have declined since World War II. Even in western Europe, with fuel prices averaging more than $ 1 a liter(about $ 4 a gallon)and with easily accessible mass transit and dense populations, cars still account for 80 percent of all passenger travel.
    Improved energy efficiency is also appealing, but automotive fuel economy has barely made any progress in 10 years. Alternative fuels such as natural gas, burned in internal-combustion engines, could be introduced at relatively low cost, but they would lead to only marginal reductions in pollution and greenhouse emissions(especially because oil companies are already spending billions of dollars every year to develop less polluting types of gasoline).
Which of the following is practical but only makes a marginal contribution to solving the problem of greenhouse emissions?

选项 A、The use of fuels other than gasoline.
B、Improved energy efficiency.
C、The introduction of less polluting driving systems.
D、Reducing car use by carpooling.

答案A

解析 本题问下列哪一项措施对于解决温室效应虽然有用但效果不大。文章第3段谈到这个问题,第3段第2句说:替代性燃料如天然气,在内燃机中燃烧可以降低消耗,但是对于减少污染和温室效应只能起到很小的作用。故选A项。
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