首页 - 网校 - 万题库 - 美好明天 - 直播 - 导航
您现在的位置: 考试吧 > 英语四六级考试 > 学习资料 > 英语四级 > 阅读 > 正文

2017年6月大学英语四级阅读练习题及答案(6)

来源:考试吧 2016-12-31 8:46:38 要考试,上考试吧! 英语四六级万题库
考试吧整理“2017年6月大学英语四级阅读练习题及答案”,更多关于英语四级阅读题、英语四级阅读技巧,请访问考试吧英语四六级考试网。

  点击查看:2017年6月大学英语四级阅读练习题及答案汇总

提醒:下载四六级万题库立即进入刷题模式>>

  Questions 61-65 are based on the following passage.

  A useful definition of an air pollutantis a compound added directly or indirectly by humans to the atmospherein suchquantities as to affect humans, animals, vegetation, or material adversely (有害地.. Air pollution requires avery flexibledefinition that permits continuous change. When the first air pollution lawswere established inEngland in the fourteenth century, air pollutants werelimited to compounds that could be seen or smelled—a farcry (悬殊的差别. from the extensive list of harmful substances known today. Astechnology has developed andknowledge of the health aspects of variouschemicals has increased, the list of air pollutants has lengthened. Inthefuture, even water vapor (水蒸气. might be consideredan air pollutant under certain conditions.

  Many of the more important airpollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides,arefound in nature. As the Earth developed, the concentrations ( 浓度. of these pollutants were altered byvariouschemical reactions; they became components in biogeochemical (生物地球化学的. cycles. These serve as an airpurification scheme by allowing thecompounds to move from the air to the water or soil. On a global basis,nature'soutput of these compounds dwarfs that resulting from human activities. However,human productionusually occurs in a localized area, such as a city.

  In this localized region, human outputmay be dominant and may temporarily overload the natural purificationscheme ofthe cycles. The result is an increased concentration of noxious ( 有害的. chemicals in the air. Theconcentrations atwhich the adverse effects appear will be greater than the concentrations thatthe pollutants wouldhave in the absence of human activities. The actualconcentration need not be large for a substance to be apollutant; in fact thenumerical value tells us little until we know how much of an increase thisrepresents over the concentration that would occur naturally in the area. Forexample, sulfur dioxide has detectable health effects at0.08 parts per million(ppm., which is about 400 times its natural level.Carbon monoxide, however, has a naturallevel of 0.1 ppm and is not usually apollutant until its level reaches about 15 ppm.

  61、It can be inferred from thefirst paragraph that _________

  A.water vapor is an air pollutant in localized areas

  B.the definition of air pollution will continue to change

  C.a substance becomes an air pollutant only in cities

  D.most air pollutants today can be seen or smelled

  62、In what way can naturalpollutants play an important role in controlling air pollution?

  A.They function as part of a purification process.

  B.They are dwarfed by the pollutants produced by human activities.

  C.They are less harmful to living beings than are other pollutants.

  D.They have existed since the Earth developed.

  63、According to the passage,the numerical value Of the concentration level of a substance is only useful if

  A.the other substances in the area are known

  B.it is a localized area

  C.it can be calculated quickly

  D.the naturally occurring level is also known

  64、Which of the following isbest supported by the passage?

  A.To effectively control pollution, local government should regularlyrevise the air pollution laws.

  B.One of the most important steps in preserving natural lands is tobetter enforce air pollution laws.

  C.Scientists should be consulted in order to establish uniform limitsfor all air pollutants.

  D.Human activities have great impact on air pollution.

  65、The passage mainlydiscusses _________

  A.the economic impact on air pollution

  B.how much damage air pollutants can cause

  C.what constitutes an air pollutant

  D.the quantity of compounds added to the atmosphere

  答案解析:

  61-65 BADDB

长按二维码关注即可顺利获得425分
获取2017最新考试资讯
获取2017最新作文预测
获取历年考试真题试卷
获取2017一次通关技巧

英语四六级题库手机题库下载】 | 微信搜索"考试吧英语四六级"

  相关推荐:

  2011-2016英语四级真题及答案|解析|估分|下载

  考试吧收藏:历年英语四级真题听力(含MP3)汇总

  1995-2016年12月英语四级作文真题及范文汇总

  四六级万题库 历年真题视频解析 立即体验

0
收藏该文章
0
收藏该文章
文章责编:zhangyuqiong  
看了本文的网友还看了
文章搜索
万题库小程序
万题库小程序
·章节视频 ·章节练习
·免费真题 ·模考试题
微信扫码,立即获取!
扫码免费使用
英语四级
共计423课时
讲义已上传
30206人在学
英语六级
共计313课时
讲义已上传
20312人在学
阅读理解
共计687课时
讲义已上传
5277人在学
完形填空
共计369课时
讲义已上传
13161人在学
作文
共计581课时
讲义已上传
7187人在学
推荐使用万题库APP学习
扫一扫,下载万题库
手机学习,复习效率提升50%!
版权声明:如果英语四六级考试网所转载内容不慎侵犯了您的权益,请与我们联系800@exam8.com,我们将会及时处理。如转载本英语四六级考试网内容,请注明出处。
Copyright © 2004- 考试吧英语四六级考试网 出版物经营许可证新出发京批字第直170033号 
京ICP证060677 京ICP备05005269号 中国科学院研究生院权威支持(北京)
精选6套卷
8次直播课
大数据宝典
通关大法!