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 pollut
It didn’t happen overnight. The problem of polluted air has been festering for centuries. Suddenly the problem of air pollut
admin
2015-01-09
71
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 re-spond 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 pol-lutant,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 envimn-mental 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.
Air pollution causes the most damage to____.
选项
A、hardwoods
B、conifers
C、fruit trees
D、fluorides
答案
B
解析
题目问:空气污染对什么树木的损害最大?第五段“To conifers,…and other environmentalstress-es.Death often follows.”第六段“air pollution injury to hardwoods may not be 80 severe”通过这句话可知,空气污染对树木有影响,针叶林往往会死掉,但对阔叶林的损害就不那么严重。据此判断,应选择B。
转载请注明原文地址:https://kaotiyun.com/show/nhLO777K
0
考博英语
相关试题推荐
Bigcitiestodayareconfrontedwithveryseriousproblems.Transportisa【1】difficulty:someplannersbelievein【2】transportsy
Bigcitiestodayareconfrontedwithveryseriousproblems.Transportisa【1】difficulty:someplannersbelievein【2】transportsy
Haveyoueverbeeninasituation______youknowtheotherpersonisrightyetyoucannotagreewithhim?
Heistheonlypersonwhocan______inthiscase,becausetheotherwitnesseswerekilledmysteriously.
Themostexcitingkindofeducationisalsothemostpersonal.Nothingcan【1】thejoyofdiscoveringforyourselfsomethingthat
Themostexcitingkindofeducationisalsothemostpersonal.Nothingcan【1】thejoyofdiscoveringforyourselfsomethingthat
Recentlyscientistshavebeen【1】andperfectingothersourcesofenergy:nuclearoratomicpower,solar(sun)power,andsynthetic(
Recentlyscientistshavebeen【1】andperfectingothersourcesofenergy:nuclearoratomicpower,solar(sun)power,andsynthetic(
随机试题
化脓性关节炎与急性痛风性关节炎的区别是
膜性肾小球肾炎的主要病理特点是
关于通信市场,下列说法不正确的是()。
法国新古典主义画家大卫的作品《__________》,表达作者对遇刺战友的崇敬。
下列叙述错误的一项是()。
2015年中央一号文件首次提出农村法治建设,以下属于加强农村法治建设措施的是()。
下面关于胶原酶的说法错误的是()。
晴朗的夜晚我们可以看到满天星斗,其中有些是自身发光的恒星,有些是自身不发光但可以反射附近恒星光的行星。恒星尽管遥远,但是有些可以被现有的光学望远镜“看到”。和恒星不同,由于行星本身不发光,而且体积远小于恒星,所以,太阳系外的行星大多无法用现有的光学望远镜“
以下关于函数的叙述中正确的是()。
IfIamnot_____whenyoucometomyoffice,askformysecretary.
最新回复
(
0
)