GRE阅读题目解析:机动车尾气排放导致空气污染

　　P48

　　1

　　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.

　　尽管近年来单体机动车的有害排放物显著降低，但机动车总数一直稳步增加，结果是，美国超过 100 座城市的一氧化碳，有害悬浮颗粒，臭氧(机动车尾气与碳氢化合物发生光化学反应的产物)水平超过法定标准。

　　2

　　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.

　　越来越多人相信唯一有效的减排方案 —— 除了私家车大规模减少 —— 就是用更清洁的燃料替换传统柴油和汽油，比如压缩天然气，液化石油气，乙醇，或甲醇。

　　(short of 此处为介词，除了，除非，other than)

　　3

　　All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline.

　　这些替代燃料与汽油同属碳基燃料，但分子更小更简单。

　　4

　　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.

　　这些分子比汽油燃烧更干净，某种程度上是因为它们含有更少的，如果有的话，碳碳键，且它们释放的碳氢化合物更不易产生臭氧。

　　5

　　The combustion of larger molecules, which have multiple carbon-carbon bonds, involves a more complex series of reactions.

　　大分子的氧化，会产生复合碳碳键，涉及更复杂的反应。

　　(不懂化学，翻错的话，请擅长化学的同学留言指导)

　　6

　　These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere.

　　这些反应增加了不充分燃烧的可能性，也更可能向大气中释放未氧化且具有光化学反应活性的碳氢化合物。

　　7

　　On the other hand, alternative fuels do have drawbacks.

　　另一方面，替代燃料也有劣势。

　　8

　　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.

　　压缩天然气需要车辆加装一组沉重的油箱 —— 难以实施也影响效率 —— 而液化石油气面临严重的供给限制。

　　9

　　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.

　　乙醇和甲醇，另一方面，相对于其他碳基替代燃料有重要优势：单位体积所产生的能量更高，且对现有配给网络秩序做出最小改动。

　　10

　　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.

　　乙醇通常被用作一种汽油的补充，但当前价格大概是甲醇的两倍，价格低是甲醇的一大优势。

　　11

　　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.

　　然而甲醇的最大优势，是能够减少机动车 90% 生成臭氧的排放，臭氧是最严重的城市空气污染物。

　　12

　　Like any alternative fuel, methanol has its critics.

　　和任何一种替代燃料一样，甲醇也受到批评。

　　13

　　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.

　　而批评大多基于市面上的车都是烧汽油的， 没有针对可能转而使用甲醇做出任何设计上的改进。

　　(yet 当 yet 引导让步关系时，可以替换为 nevertheless，引导被强调的内容(与之相对地，although 引导被让步的内容)。

　　gasoline clone 不知道怎么翻译，意会吧。X clone 指一系列有某种共同特点的事物。)

　　14

　　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.

　　的确，比如说，甲醇只能提供相同体积的汽油或柴油燃料一半的能量;其他条件相同，(烧甲醇燃料的汽车)油箱会变得更大也更重。

　　15

　　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.

　　然而，因为烧甲醇燃料的车可以被设计得 比烧汽油的车烧甲醇 更有效率，所以它们相对省油。

　　16

　　Vehicles incorporating only the simplest of the engine improvements that makes methanol feasible would still contribute to an immediate lessening of urban air pollution.

　　对发动机做出最简单的改进，使车可以烧甲醇，仍可以帮助减少城市空气污染。

　　(原 that methanol makes feasible 改为 that makes methanol feasible)

　　1. According to the passage, incomplete combustion is more likely to occur with gasoline than with an alternative fuel because

　　A. the combustion of gasoline releases photochemically active hydrocarbons

　　B. the combustion of gasoline involves an intricate series of reactions

　　C. gasoline molecules have a simple molecular structure

　　D. gasoline is composed of small molecules.

　　E. gasoline is a carbon-based fuel

　　选 B

　　细节题。

　　根据句 5 - 6：

　　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.

　　2. Which of the following most closely parallels the situation described in the first sentence of the passage?

　　A. Although a town reduces its public services in order to avoid a tax increase, the town’s tax rate exceeds that of other towns in the surrounding area.

　　B. Although a state passes strict laws to limit the type of toxic material that can be disposed of in public landfills, illegal dumping continues to increase.

　　C. Although a town’s citizens reduce their individual use of water, the town’s water supplies continue to dwindle because of a steady increase in the total population of the town.

　　D. Although a country attempts to increase the sale of domestic goods by adding a tax to the price of imported goods, the sale of imported goods within the country continues to increase.

　　E. Although a country reduces the speed limit on its national highways, the number of fatalities caused by automobile accidents continues to increase.

　　选 C

　　句 1：

　　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.

　　其特征可以概括为，从个体看形势在好转，但整体形势恶化。

　　C 正确。尽管小镇居民个人用水量减少(节约)，但总人口不断增加导致水供应紧张逐渐加剧(整体恶化)。

　　其他几项有不解的来留言。

　　3. It can be inferred from the passage that a vehicle specifically designed to use methanol for fuel would

　　A. be somewhat lighter in total body weight than a conventional vehicle fueled with gasoline

　　B. be more expensive to operate than a conventional vehicle fueled with gasoline

　　C. have a larger and more powerful engine than a conventional vehicle fueled with gasoline

　　D. have a larger and heavier fuel tank than a “gasoline clone” vehicle fueled with methanol

　　E. average more miles per gallon than a “gasoline clone” vehicle fueled with methanol

　　选 E

　　根据句 15：

　　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.

　　你脑子里得有概念，这是三种效率。

　　A 汽油车烧汽油。

　　B 汽油车烧甲醇。

　　C 改装车烧甲醇。

　　单纯比较效率 A > C > B 。但文章开头就说 A 引起环境问题，所以就算效率高，也不考虑了，这句话比较的是 B 和 C，结论是 C 相对效率更高，更省油。

　　所以选 E 。

　　4. The passage suggests which of the following about air pollution?

　　A. Further attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels.

　　B. Attempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful.

　　C. Few serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles.

　　D. Pollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution.

　　E. Reductions in pollutants emitted by individual vehicles have been offset by increases in pollution from sources other than gasoline-fueled vehicles.

　　选 A

　　关照文章前两句，参考第二题的分析，虽然个体被优化，但整体不断恶化，所以继续在个体减排方面努力已经无法治理污染了，得换燃料了。

　　B 错。个体减排是成功的，第一句有 substantial reductions in noxious pollutants from individual motor vehicles 。

　　C 错。不但尝试了，而且能尝试的都尝试了，所以人们才开始从其他方向想解决办法。

　　D 错。句 11 告诉我们臭氧是最严重的污染源 ozone, the most serious urban air pollutant 。而文章开头就告诉我们臭氧超标，与机动车排放有关。

　　E 错。没人选这个吧，选这个的来跟我聊聊，好奇。

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