首页
登录
职称英语
Although recent years have seen substantial reductions in noxious pollutants
Although recent years have seen substantial reductions in noxious pollutants
游客
2023-08-23
46
管理
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. [br] The author of the text is primarily concerned with______.
选项
A、countering a flawed argument that dismisses a possible solution to a problem
B、reconciling contradictory points of view about the nature of a problem
C、identifying the strengths of possible solutions to a problem
D、discussing a problem and arguing in favour of one solution to it
答案
C
解析
主旨题。本章第一段首先提出车辆废气的问题,然后指出实现车辆废气进一步减少而又不必大规模减少私家轿车的唯一有效途径是用清洁燃料来代替传统的柴油和汽油燃料。而在其他段落分别介绍了压缩天然气、液化石油气、乙醇和甲醇的优势和可行性。可知文章的思路是分析一个问题的可能解决方案的优势,和C选项表达一致。所以答案选C。
转载请注明原文地址:https://tihaiku.com/zcyy/2949628.html
相关试题推荐
[originaltext]Recentlyafive-yearstudywasconductedbytheCenterforCh
[originaltext]Recentlyafive-yearstudywasconductedbytheCenterforCh
[originaltext]Recentlyafive-yearstudywasconductedbytheCenterforCh
[originaltext]Recentlyafive-yearstudywasconductedbytheCenterforCh
[originaltext]Therecentincreaseincarstealinghasalarmedthepolicewh
[originaltext]Inthecaseofmobilephones,changeiseverything.Recentre
Althoughwealreadyknowagreatdealaboutinfluenza,itisdifficultfore
Althoughwealreadyknowagreatdealaboutinfluenza,itisdifficultfore
Althoughwealreadyknowagreatdealaboutinfluenza,itisdifficultfore
Althoughwealreadyknowagreatdealaboutinfluenza,itisdifficultfore
随机试题
暗期光间断一般要求较高强度的光照。
某期货公司任命王某为本公司的首席风险官,下列关于王某开展工作的做法中,正确的是(
以下关于回购协议市场说法不正确的是()。A.我国存在两个分离的国债回购市场
护理人员常咨询的药学信息问题是A.药物的选择和替换B.药品的市场情况C.药品配伍
A. B. C. D.
预应力混凝土应优先采用( )水泥。A.火山灰质硅酸盐 B.硅酸盐 C.矿渣
关于发达国家和地区工程造价管理的特点,下列说明中正确的是()。A.美国的E
下列施工临时用电的变化,不需要变更用电合同的是()。A.减少合同约定的用电
男,20岁。持续性左上腹痛2小时。查体:T38.7℃,P128/分,R24
A.色泽较白,质黏稠,含大量白细胞 B.有血腥味,但无臭味,持续4~6周 C
最新回复
(
0
)