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
It didn’t happen overnight The problem of polluted air has been festering for centuries. Suddenly the problem of air polluti
It didn’t happen overnight The problem of polluted air has been festering for centuries. Suddenly the problem of air polluti
admin
2013-01-28
63
问题
It didn’t happen overnight The problem of polluted air has been festering for centuries.
Suddenly the problem of air pollution is becoming critical and is erupting right before our eyes. Not only do our eyes burn as they focus through murky air, but when the air clears, we see trees and vegetation dying. We must realize that this destruction can no longer be pinned to some mysterious cause. The one major culprit is air pollution.
Today’s air pollution is an unfortunate by-product of the growth of civilization. Civilized mall desires goods that require heavy industrialization and mass production. Machines and factories sometimes pollute and taint the air with substances that are dangerous to man and the environment These substances include radioactive dust, salt spray, herbicide and pesticide aerosols, liquid droplets of acidic matter, gases, and sometimes soil particles. These materials can act alone to irritate objects and forms of life. More dangerously, they join together to act upon the environment Only lately have we begun recognizing some of their dangerous consequences.
Scientists have not yet been able to obtain a complete report on the effects of air pollution on trees. They do know, however, that sulfur dioxide, fluorides, and ozone destroy trees and that individual trees respond differently to the numerous particulate and gaseous pollutants. Sometimes trees growing in a single area under attack by pollutants will show symptoms of injury or will die while their neighbors remain healthy. Scientists believe this difference in response depends on the kind of tree and its genetic makeup. Other factors, such as the tree’s stage of growth and nearness to the pollution source, the amount of pollutant, and the length of the pollution attack also play a part In short, whether or not a tree dies as a result of air pollution depends on a combination of host and envimnmental factors.
For the most part, air pollutants injure trees. To conifers, which have year-round needles, air pollution causes early balding. In this event, trees cannot maintain normal food production levels. Undernourished and weakened, they are open to attack by a host of insects, diseases, and other environmental stresses. Death often follows.
Air pollution may also cause hardwoods to lose their leaves. Because their leaves are borne only for a partion of the year and are replaced the following year, air pollution injury to hardwoods may not be so severe.
We can conclude that______.
选项
A、air pollution is easier to control than water pollution
B、the problem of polluted air is a problem overnight
C、the impact of air pollution has been known for centuries
D、research on the efforts of air pollution is incomplete
答案
D
解析
文章指出,关于空气污染对树木的影响问题,科学家还没有得到完整的结论。第四段第一句Scientists have not yet been able to obtain a complete report on the effects of air pollution on trees.
转载请注明原文地址:https://kaotiyun.com/show/D81O777K
0
考博英语
相关试题推荐
Islanguage,likefood,abasichumanneedwithoutwhichachildatacriticalperiodoflifecanbestarvedanddamaged?Judgin
Oneofthemostauthoritativevoicesspeakingtoustodayisthevoiceoftheadvertisers.Itsstridentclamourdominatesourli
Don’tcallhimjustacollegeprofessor.Internetentrepreneur,TVpersonality,advisortopresidents,andfriendtotherichan
IwasvisitingNewYorklastweekandnoticedsomethingI’dneverthoughtI’dsayaboutthecity.Yes,nightlifeisprettymuch
IwasvisitingNewYorklastweekandnoticedsomethingI’dneverthoughtI’dsayaboutthecity.Yes,nightlifeisprettymuch
Whatismeant【51】theword"friend"?Thedictionary【52】itas:."oneattachedto【53】byaffectionoresteem".Americansuset
InNovember1970YukioMishima,togetherwithsomeofhisfanaticalfollowersfromtheultranationalisticShieldSocietywhichh
EnglishasaworldLanguageEnglishisavictimofitsownsuccess.NewspapersinEnglandhavenoticedthattheincorrectus
Well,nogainwithoutpain,theysay.Butwhataboutpainwithoutgain?EverywhereyougoinAmerica,youheartalesofcorporat
随机试题
某蛋白质有100个氨基酸残基,其基因有2个外显子。外显子之间相隔100bp,其mRNA5’和3’端分别有70个和30个核苷酸的不翻译区段,从该成熟mRNA获得的cDNA大小与其相符的是
合理用药的意义在于
决定传染病病人隔离期限长短的主要依据是
A.散热率B.额定容量C.瞬间负荷D.连续负荷E.阳极热容量X线管连续使用下阳极的热量积累的最大允许值称为
治疗癥瘕积块应遵循的原则是
女性,30岁。因宫外孕破裂大出血入院。体检面色苍白,脉搏140次/分,血压60/40mmHg。为防止发生过敏反应,输血前应皮下注射抗过敏药物。下列操作方法中错误的是
下列内容中属于经济法律关系客体的有( )。
教育的本质是______.
I’dratheryou_________anythingaboutitforthetimebeing.
【S1】【S6】
最新回复
(
0
)