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
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantitie
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantitie
admin
2022-10-23
44
问题
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled—a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulfur oxides (硫氧化物), carbon monoxide, and nitrogen oxides, are found in nature. As the earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles. These 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 that resulting from human activities. However, human production usually occurs in a localized area, such as a city.
In this localized region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effect appears will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact the numerical value 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 (ppm), which is about 400 times its natural level. Carbon monoxide, however, has natural level of 0. 1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
From the first paragraph, we can infer that________.
选项
A、water vapor is an air pollutant in localized areas
B、today most air pollutants can be seen or smelled
C、the definition of air pollution will continue to change
D、a substance becomes an air pollutant only in cities
答案
C
解析
由题干关键词the first paragraph定位至第一段。推理判断题。由第一段第二句可知,C“空气污染的定义会继续改变”与文章表述一致,而且文中也详细说明了这一变化情况,故C为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/UGR7777K
0
大学英语六级
相关试题推荐
A、Theyaretargetingatyoungpeople.B、Theycanleadtoeatingdisorders.C、Theycancuresomeskinproblems.D、Theyarepersua
A、Everybodywillfeelcentered.B、Nobodywillgetbored.C、Nobodywillbeexcluded.D、Everybodywilltalkalot.C
A、Everybodywillfeelcentered.B、Nobodywillgetbored.C、Nobodywillbeexcluded.D、Everybodywilltalkalot.C
A、TheimportantrolethatInternetplaysinhumanlife.B、TheadvantagesoftheInternetandthecomputer.C、Theinfluenceofth
A、Travelaloneonthecrowdedstreets.B、Travelwithabodyguardtoprotectthemselves.C、Carryanoteinthelanguageofthefo
Humansarefascinatedbythesourceoftheirfailingsandvirtues.Thispreoccupationinevitablyleadstoanolddebate:whether
A、Travelaloneonthecrowdedstreets.B、Travelwithabodyguardtoprotectthemselves.C、Carryanoteinthelanguageofthefo
A、Watermightbecomecleanandpure.B、Peoplewillliveinabetterenvironment.C、Therewillbenopolicetoprotectpeople.D、
随机试题
苦味药所含的主要成分是
女,58岁,腹痛腹胀1年余,结合图像,最可能的诊断为
出口国家重点保护的野生动植物及产品或者我国参加的国际公约所限制进出口的野生动植物及产品以及含有野生动植物成分的产品,必须经中华人民共和国濒危物种进出口管理办公室核准,并取得其核发的(),进出口单位凭此向海关报验。
证券公司开展集合资产管理业务,应当遵循以下( )等方面的业务规范。
下列对货币市场的特征描述正确的是()。
对广告接触者的数量、接触者的范围、广告接触频次的测评,叫做()。
行车途中,地陪导游员可以组织活动来活跃车内气氛,但()就不合适。
—Couldyoutellme______?—Sure.Inthepostofficeongreenstreet.
假设下面的市场模型充分描述了风险资产收益产生的方式:Rit=αi+βiRMt+εit,其中,Rit是第i种资产在时间t的收益;RMt是一个以某种比例包括了所有资产的投资组合在时间t的收益。RMt和εit在统计上是独立的。市场允许卖空(即持有量为负)。你所拥
Ifyougodowntothewoodstoday,youmaymeethigh-techtrees-geneticallymodifiedtospeedtheirgrowthorimprovethequalit
最新回复
(
0
)