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
Narrator Listen to part of a talk in an environmental science class. Now get ready to answer the questions. You may use
Narrator Listen to part of a talk in an environmental science class. Now get ready to answer the questions. You may use
admin
2013-04-25
28
问题
Narrator
Listen to part of a talk in an environmental science class.
Now get ready to answer the questions. You may use your notes to help you answer.
What does the professor mean when he says this?
How much can you say about air pollutant? At first let’s have a look at a useful definition of it. A pollutant is a compound added directly or indirectly by humans to the atmosphere, and in such quantities to adversely affect humans, animals, vegetations or materials. On the other hand air pollution has a very flexible definition that allows continuous change. When the first air pollution law was established in England in the 14th century, air pollutants were limited to compounds that could be seen or smelled, which is very different from the list of harmful substances known today. As technology has developed and knowledge of health aspects has increased, the list of air pollutants has lengthened. In the future even water vapor might be thought of as an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides are found in nature. Perhaps in your daily life you can’t feel them clearly since they don’t make up a big percentage of the air. Before we have learnt something about the properties of the above substances, let’s have a look at their historical development. As the earth developed, the concentrations of these pollutants were altered by various chemical reactions and become biogeochemical components, and then they serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature’s output of these compounds dwarfs those resulting from human activities. However, human production usually occurs in a localized area, such as a city.
In these localized regions, human output may be dominant and may temporarily overload the natural purification scheme of cycles. The result is an increased concentration of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact the concentration tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0.08 parts per million, often shortened to ppm, which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
选项
A、Little is known about defining a substance as an air pollutant.
B、The substance isn’t an air pollutant when there is a very little in the air.
C、The substance can’t be judged to be an air pollutant only from its actual concentration level.
D、The actual concentration level means little to peopl
答案
C
解析
本题为语用理解题,考查考生是否能听懂说话者说话的意图。题目问:教授说这一段话是什么意思?原文第三段提到“The actual concentration need not be large for a substance to be a pollutant; in fact the concentration tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area”,这段话的大意是:只有知道这种物质的实际含量比空气中的自然含量增加了多少才能断定它是不是污染物,因此C项为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/AdyO777K
0
托福(TOEFL)
相关试题推荐
Theprofessorwantsthestudentstopretendthattheyare______.
Theprofessorwantsthestudentstopretendthattheyare______.
Theprofessorwantsthestudentstopretendthattheyare______.
Questions39-40AnswerthefollowingquestionsusingNOMORETHANTHREEWORDSforeachanswer
Thestudentsayssheis______whensheisstudyingathome.Theadvisersuggests______withanotherstudentafterlectureso
Qusetions11-15AnswerthefollowingquestionsusingNOMORETHANTHREEWORDSAND/ORANUMBERforeachanswer.
Completethesummarybelow.UseNOMORETHANTHREEWORDSforeachanswer.PROJECTMANAGENTLastweek’sdefinitionofpro
Completethesummarybelow.UseNOMORETHANTHREEWORDSforeachanswer.PROJECTMANAGENTLastweek’sdefinitionofpro
随机试题
工作评价的方法包括()
A.肾脏淀粉样变性B.肾小管酸中毒C.局灶节段坏死性肾小球肾炎D.小动脉内皮细胞增生类风湿关节炎最终导致的主要肾脏病变为
A.西地那非B.普适泰C.特拉唑嗪D.非那雄胺E.奥昔布宁用于前列腺增生症的M受体阻断剂()。
甲将私家车借给无驾照的乙使用。乙夜间驾车与其叔丙出行,途中遇刘某过马路,不慎将其撞成重伤,车辆亦受损。丙下车查看情况,对乙谎称自己留下打电话叫救护车,让乙赶紧将车开走。乙离去后,丙将刘某藏匿在草丛中离开。刘某因错过抢救时机身亡。(事实一)为逃避刑
根据《建设工程安全生产管理条例》,属于施工单位安全责任的有()。
按《水利水电基本建设工程单元工程质量评定标准》,单元工程质量标准项目可分为一般原则和要求、质量检查项目和()。
国有股权无偿划转的,满足以下( )条件的,可以视为控制权没有发生变更。
下列哪些属于绍剧的传统曲目?()
公元前356年和前350年,()先后两次任用商鞅进行变法。
∫x/(1+x4)dx=________.
最新回复
(
0
)