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
66
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.
The resistance of some trees to disease can be traced to______.
选项
A、protective foliage
B、thick bark
C、genetic makeup
D、tainted air
答案
C
解析
文章指出,科学家认为,树木对疾病的不同反应取决于树的种类和遗传因素。第四段Scientistsbelieve this difference in response depends on the kind of tree and its genetic makeup.
转载请注明原文地址:https://kaotiyun.com/show/C81O777K
0
考博英语
相关试题推荐
The______friendwasexposedintheendtobehiddenrivalwhohadbeenplottingagainstthecompany’smarketinginHongKong.
Oneofthemostauthoritativevoicesspeakingtoustodayisthevoiceoftheadvertisers.Itsstridentclamourdominatesourli
Oneofthemostauthoritativevoicesspeakingtoustodayisthevoiceoftheadvertisers.Itsstridentclamourdominatesourli
Theinternationalsituationhasbeengrowing______difficultforthelastfewyears.
Fewpeopledoubtthefundamentalimportanceofmothersinchild-rearing,butwhatdofathersdo?Muchofwhattheycontributeis
Whatismeant【51】theword"friend"?Thedictionary【52】itas:."oneattachedto【53】byaffectionoresteem".Americansuset
Whatismeant【51】theword"friend"?Thedictionary【52】itas:."oneattachedto【53】byaffectionoresteem".Americansuset
EnglishasaworldLanguageEnglishisavictimofitsownsuccess.NewspapersinEnglandhavenoticedthattheincorrectus
ThetwopsychologistshadtomodifytheAmericanSignLanguagesomewhatinordertoaccommodatethechimpanzees’spontaneousges
WiththeUSeconomyslowingdown,layoffsareeverywhere.Noindustryisspared.Ifyouenduphavingtostartover,inaddition
随机试题
我们采纳西蒙兹等学者对不同父母教养方式的阐释,利用“关爱”和“权威”两个向度可以交互组合成_________、绝对权威型、娇惯溺爱型和忽视冷漠型四个主要的教养类型。
肺性脑病:
A.生脉散B.归脾汤C.金匮肾气丸D.消渴方E.桃红四物汤治疗糖尿病气滞血瘀型,应首选
在基本的量本利图中,销售收入线与总成本线的交点是盈亏平衡点,这个点也称为()。
下列各项中,应列入“支付给职工以及为职工支付的现金”项目的是()。
德州市东方朔画赞赞文曾由()三次书写。
人眼的光学系统跟传统的照相机是十分类似的。但照相机只是把外界景物的图像映在照相软片上,人眼却并不是把投射到视网膜上的图像______________地传给大脑,而是先对图像进行信息加工,抽取线段、角度、弧度、色度和明暗对比等包含重要信息的简单特征,并把它们
一位研究人员希望了解他所住小区的人们喜欢的是纯甄酸奶还是安慕希酸奶,他随机抽取一些品尝常温酸奶的人,要他们通过品尝指出喜欢的类型,为避免商标引发的偏见,酸奶的外壳商标被遮挡,“A”表示纯甄酸奶,“B”表示安慕希酸奶,结果显示,超过一半的人更喜欢纯甄酸奶,而
有些群众生活困难,虽有发展潜力,但现在难以靠自己改变目前的处境,需要扶一把。有人认为,资源和就业的配置要通过市场解决,政府不好包办,但市场不可能自动实现社会收入的公平与协调,也不可能顾及全社会的扶贫救弱,假如困难群体陷于无助,贫富差距过大,无疑会影响社会的
定义部门关系模式:部门(部门号,部门名,部门成员,部门总经理),使它不满足第一范式的属性是
最新回复
(
0
)