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
2015-01-31
29
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.
According to the text, incomplete combustion is more likely to occur with gasoline than with an alternative fuel because______.
选项
A、the combustion of gasoline releases photochemically active hydrocarbons
B、the combustion of gasoline embraces an intricate set of reactions
C、gasoline molecules have a simple molecular structure
D、gasoline is composed of small molecules
答案
B
解析
细节题。根据incomplete combustion将答案定位到第二段The combustionof larger molecules,which have multiple carbon-carbon bonds involves a more complexseries of reactions.These reactions increase the probability of incomplete combustionand are more likely to release uncombusted and photochemically active hydrocarboncompounds into the atmosphere.“那些具有多重碳一碳化学键的大分子在燃烧时包含了一系列复杂的反应。这些反应增大了不完全燃烧的可能,并且更容易释放未燃烧的碳氢化合物,而这些化合物又对光化学反应很活跃。”可知不完全燃烧的出现是因为汽油的燃烧包含了一系列复杂的反应,和选项B的表述一致。所以答案选B。
转载请注明原文地址:https://kaotiyun.com/show/aFh7777K
0
大学英语六级
相关试题推荐
A、Mainlybecauseshefeltnervousonthestage.B、Mainlybecauseshelostherinterestinthatrole.C、Mainlybecausesheprefer
A、Interested.B、Indifferent.C、Suspicious.D、Negative.D女士建议男士选择坐游轮去希腊或者土耳其旅行,男士说味道油腻的食物不合自己的胃口,言下之意就是不接受这个建议,故选D。
A、Inanoffice.B、Inarestaurant.C、Inadepartmentstore.D、Inafactory.D男士问:“谁将糖果装入盒子里?”,女士话中的“自动计数”,“机器”以及“我马上带你去看”,表明对话发生
ImprovingthebalancebetweentheworkingpartofthedayandtherestofitisagoalofagrowingnumberofworkersinrichWe
A、Thebodywilltakeinmoreoxygen.B、Theheartwillbeatmorefrequently.C、Muscleswillbecometenseandthebodywillsweat
Isyourfamilyinterestedinbuyingadog?Adogcanbeahappy【B1】______toyourfamily,butifyouchoosethewrongkindofdog
AccordingtothemostrecentAmericanFreshmansurvey,conductedannuallybytheUniversityofCalifornia,LosAngeles,undergra
A、Trafficaccidents.B、Radiation.C、Traintravel.D、Aircrash.B原文提及“不久前人们认为在太空中会遭遇到严重的威胁,主要有辐射和流星撞击”。故B正确。
A、Heisaniceguy.B、Hehasprettyears.C、Heisveryhelpful.D、Heisverytalkative.D
随机试题
如果指示剂的变色范围全部处于滴定突跃之内,则滴定误差最小。
黄疸的病理因素有湿邪、热邪、寒邪、疫毒、气滞、瘀血六种。但其中以哪个为主
两样本均数比较的检验,差别有显著性,时,P越小,说明
患者女,13岁,正在进行正畸治疗,医生建议她使用氟化凝胶防龋医生叮嘱患者下次复诊时间
大肠液亏证的主症是
王某,女,1990年出生,于2012年2月1日入职某公司,从事后勤工作,双方口头约定每月工资为人民币3000元,试用期1个月。2012年6月30日,王某因无法胜任经常性的夜间高处作业而提出离职,经公司同意,双方办理了工资结算手续,并于同日解除了劳动关系。同
案例F市某C钢铁有限公司年产生铁500×104t,各类型钢等400×104t。公司下设炼铁厂、炼钢厂、烧结球团厂等分厂及安全部、设备管理部、办公室等辅助部门。现有员工6600名,其中专职安全管理人员80名。主要生产设备设施包括2×500m3、3×880m
对需要结汁本月发生额的账户,结计“过次页”的本页合计数应当为自本页第二行起至本页末止的发生额合计数。()
主办券商的代办业务包括()
用多水平法编制的弹性预算,主要特点是()。
最新回复
(
0
)