The passage suggests which of the following about air pollution?答案解析-雷哥GRE

雷哥网GRE > 阅读&逻辑 > CHP36套 > 2394

CHP36套 -2394【hard】 00:00:00 关闭计时

纠错

Although, recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing, consequently, more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing realization that the only effective way to achieve further reductions in vehicle emissions-short of a massive shift away from the private automobile-is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas, liquefied petroleum gas, ethanol, or methanol.

All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds, and the hydrocarbons they do emit are less likely to generate ozone. The combustion of larger molecules, which have multiple carbon-carbon bonds, involves a more complex series of reactions. These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere. On the other hand, alternative fuels do have drawbacks. Compressed natural gas would require that vehicles have a set of heavy fuel tanks-a serious liability in terms of performance and fuel efficiency-and liquefied petroleum gas faces fundamental limits on supply.

Ethanol and methanol, on the other hand, have important advantages over other carbon-based alternative fuels: they have a higher energy content per volume and would require minimal changes in the existing network for distributing motor fuel. Ethanol is commonly used as a gasoline supplement, but it is currently about twice as expensive as methanol, the low cost of which is one of its attractive features. Methanol`s most attractive feature, however, is that it can reduce by about 90 percent the vehicle emissions that form ozone, the most serious urban air pollutant.

Like any alternative fuel, methanol has its critics. Yet much of the criticism is based on the use of "gasoline clone" vehicles that do not incorporate even the simplest design improvements that are made possible with the use of methanol. It is true, for example, that a given volume of methanol provides only about one-half of the energy that gasoline and diesel fuel do; other things being equal, the fuel tank would have to be somewhat larger and heavier. However, since methanol-fueled vehicles could be designed to be much more efficient than "gasoline clone" vehicles fueled with methanol, they would need comparatively less fuel. Vehicles incorporating only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution.

The passage suggests which of the following about air pollution?

AFurther attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels. BAttempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful. CFew serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles. DPollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution. EReductions in pollutants emitted by individual vehicles have been offset by increases in pollution from sources other than gasoline-fueled vehicles.

正确答案： A 耗时：

该题平均耗时：2分35秒，平均正确率：53 %，难度系数：5 。该题由网友提供。更多GRE题目请点击上传

做题笔记

暂无做题笔记

网友解析

我有更好的解析

当前版本由 VERNA 更新于2018-05-09 17:10:59 感谢由 VERNA 对此题目的解答所做出的贡献。

A. 文章没提，即使提了这样说也与文意相反；
B. 文章的结构就是用老的翻译和新的 writing 进行对比，新的内容取非就是老的
特点；定位同上第六题；
C. 同样是的新的 writing 取非，定位 L6:‖ experimenting with European literary
forms‖.