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
2014-12-26
32
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 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 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 possibly 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-fuelled vehicles could be designed to be much more efficient than "gasoline clone" vehicles fuelled 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 author describes which of the following as the most appealing feature of methanol?
选项
A、It is substantially less expensive than ethanol.
B、It has a higher energy content than other alternative fuels.
C、Its use would make design improvements in individual vehicles feasible.
D、Its use would substantially reduce ozone levels.
答案
D
解析
细节题。根据methanol定位到第三段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,甲醇最吸引人的特点还在于它可以减少90%形成臭氧的废气,而臭氧又是城市中最严重的污染物。”甲醇最吸引人的特点是它可以大量减少臭氧含量,和选项D的表述一致。所以答案选D。
转载请注明原文地址:https://jikaoti.com/ti/qMgFFFFM
0
大学英语六级
相关试题推荐
A、Therewon’tbetiesinmediumenterprisesin20years.B、Mostpeoplebelievethetiewoulddisappearin10years.C、Mostpeopl
ABritishstudyhasfoundthatBvitaminscanreducebrainshrinkageinolderpeoplewithmildmemoryloss.It【B1】______thatBv
A、Acomparisonbetweenfishandwarm-bloodedanimals.B、Thedifferencebetweensaltwaterandfreshwaterenvironments.C、Theimpo
Themobilephoneissettobecomeoneofthecentraltechnologiesofthe21stcentury.Withinafewyears,themobilephonewill
Themobilephoneissettobecomeoneofthecentraltechnologiesofthe21stcentury.Withinafewyears,themobilephonewill
Themobilephoneissettobecomeoneofthecentraltechnologiesofthe21stcentury.Withinafewyears,themobilephonewill
A、Englanddidn’thaveprivateuniversitiesasAmericadid.B、Americanhighereducationwasbetterinquality.C、Englandhadmore
A、WhattheUSpatentsystemwasabout.B、HowtheUSpatentsystemencouragedtechnologyandcreativity.C、HowtheUSpatentsyst
Forthousandsofyearsmanhasexploitedandoftendestroyedtherichesofland.Nowmancovets(觊觎)thewealthoftheoceans.Eve
随机试题
人体感染下列传染病后免疫状态是A、持续免疫B、短暂免疫C、带虫免疫D、再感染E、交叉免疫细菌性痢疾()
关于肾盂移行细胞癌的CT表现,错误的是
A、清热解毒,排脓消痈B、清热解毒,祛痰利咽C、清热解毒,凉血止痢D、清热解毒,祛风燥湿E、清热解毒,活血止痛鱼腥草的功效为
混凝土护栏构件在脱底模、移动、堆放、吊装时的强度一般不得低于设计强度的70%。()
从银行提取现金时,一般应编制的记账凭证是()。
该企业自产自用和投资用的产品应纳消费税合计为()。该企业销售产品应纳的增值税和消费税合计为()。
存作业成本法下,成本动因是导致成本发生的诱因,是成本分配的依据。()
公民甲从兴华商场买了一瓶红星肉厂生产的熟食罐头,吃后中毒住院,花去住院费等共计2000元。经查,该批罐头由兴华商场委托湖月运输公司运回,该运输公司未采取冷藏措施,致使罐头有一定程度的变质。运回后兴华商场交由天天储存公司储存,天天公司也未采取冷藏措施,致使罐
下列公文的格式中,不包括主送机关的是()。
我国民事审判一般实行()。
最新回复
(
0
)