首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Although recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such
Although recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such
admin
2018-07-04
48
问题
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.
It can be inferred from the passage that a vehicle specifically designed to use methanol for fuel would
选项
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
答案
E
解析
根据专门烧甲醇的车定位到第四段第四句。第四句的同义替换是专门烧甲醇的车比“汽油克隆”车行驶一样的距离用更少的燃料,与选项E同义。
转载请注明原文地址:https://kaotiyun.com/show/vpjO777K
本试题收录于:
GRE VERBAL题库GRE分类
0
GRE VERBAL
GRE
相关试题推荐
Technologyhasbeenanencouragementofhistoricalchange.ItactedassuchaforceinEnglandbeginningintheeighteenthcentu
Both52and33arefactorsofn×25×62×73wherenisapositiveinteger.Whatisthesmallestpossiblevalueofn?
Thepassageisprimarilyconcernedwith______Accordingtothepassage,whichofthefollowingisafactorthatisthreatening
Whichofthefollowingbeststatesthecentralideaofthepassage?Whichofthefollowingdoestheauthorcitetosupportthe
Whichofthefollowing,iftrue,bestcompletesthepassagebelow?ThetraditionalviewofHomeristhatofablindbardwho
11.Calvin:Fireinsurancepoliciesaredisadvantageoustopolicyholders.Thetypicalpolicyholderalwayspaysmoreinpremiums
ThetownofGreenfieldrecentlyinstitutedasubstantialsupplementarytaxonallhouseholds,wherebyeachhouseholdistaxedin
Formanypeople,householdlaborremainsdemandingevenifabletoaffordhouseholdappliancestheirgrandparentswouldfindam
Thegrowthoftherailroadsledtotheabolitionoflocaltimes,whichwasdeterminedbywhenthesunreachedtheobserver’smer
RecentfeministscholarshipconcerningtheUnitedStatesinthe1920schallengesearlierinterpretationsthatassessedthe1920s
随机试题
检定、校准、检测依据的非标准方法指什么?举例说明。
急性痘疮样苔藓状糠疹的皮损特点是
【背景】某市政府投资一个建设项目,项目法人单位委托招标代理机构采用公开招标方式代理项目施工招标,并委托具有相应资质的工程造价咨询企业编制招标控制价。招标投标过程中发生如下事件:事件1:招标信息在招标信息网上发布后,招标人考虑到该项目建设
背景某建筑工程,基坑深17m,地下水位在基坑深度10m处,基坑支护采取地下连续墙形式,地下连续墙深35m。在施工11号槽段时,钢筋笼放入基坑,由于基坑内有大量沉渣,钢筋笼不能放入坑底,造成此槽段混凝土不能浇筑,半夜赶上暴雨,致使此槽段塌孔。此槽段紧邻正在
某施工单位筹集资金总额300万元,使用费为80万元,筹资费为50万元,则其资金成本率为()。
一般资料:求助者,男性,49岁,工人。案例介绍:求助者去年体检发现肺部阴影,经检查确诊为肺癌早期。经过半年多的治疗,病情基本稳定,各项指标也逐步恢复正常。但住院期间看到许多癌症转移复发的病友,很担忧自己的情况,于是密切观察自己的身体变化,身上长出
图2是Word所制作文档的一部分,其中剪贴画“青蛙”的文字环绕方式是()。
我们要继续锲而不舍,一以贯之抓好社会主义精神文明建设,为全国各族人民不断前进提供坚强的思想保证、强大的精神力量、丰润的道德滋养。社会主义精神文明建设的重要内容和中心环节是()。
在一段时间内有10架飞机飞过,其中6架为敌机,雷达报告到其中的5架,并把2架民用机误报为敌机。雷达的正确拒绝率为()
设a≠0为常数,f(x)可导,且满足=f(x)+x,求f(x).
最新回复
(
0
)