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
51
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
He______unwisely,buthewasatleasttryingtodosomethinghelpful.
Bigcitiestodayareconfrontedwithveryseriousproblems.Transportisa【1】difficulty:someplannersbelievein【2】transportsy
Bigcitiestodayareconfrontedwithveryseriousproblems.Transportisa【1】difficulty:someplannersbelievein【2】transportsy
Bigcitiestodayareconfrontedwithveryseriousproblems.Transportisa【1】difficulty:someplannersbelievein【2】transportsy
OneofFreud’sgreat______intothehumanpersonalitywasthediscoveryofhowitisinfluencedbyunconsciousprocesses.
TheUNofficialsaidaidprogramswillbe______untilthereisadequateprotectionforreliefpersonnel.
Themostexcitingkindofeducationisalsothemostpersonal.Nothingcan【1】thejoyofdiscoveringforyourselfsomethingthat
Bysuchdemarcation,strong,representativenationalsocietiescanthenbelefttodowhattheydobest—______youngscientists’d
Theconceptofinternet,______hasintriguedscientistssincethemid-20thcentury.
随机试题
Marynevertellsanyonewhatshedoesfora______.
IoncewenttoatowninthenorthofEnglandonbusiness.Itwasabout7:30intheeveningwhenIreachedthehotel.Thema
男,67岁,牙列缺失,在正中关系位时,上颌轻度前突,排前牙的正确方法是A.上、下颌人工牙均向唇侧排B.上、下颌人工牙均向舌侧排C.上颌人工牙略向舌侧排,下颌人工牙略向唇侧排D.上颌人工牙略向唇侧排,下颌人工牙略向舌侧排E.上、下颌人工牙均排在牙槽
45岁妇女,性交后出血就诊。检查宫颈中度糜烂,子宫正常大小、活动,宫旁(-),宫颈刮片巴氏Ⅲ级。最合适的辅助检查是哪项
男性,26岁。发生左侧腹部及左下胸部撞击伤3小时。检查:神志清,T37℃,BP80/60mmHg,P120次/分。左侧腹压痛,有轻度反跳痛及肌紧张,血白细胞20×109/L。尿镜检红细胞20个/HP,正确的急救处理是
A公司赊销一批商品,货款60000元(不含增值税额),商业折扣为10%,货款尚未收到。客户可享有2/10,1/20,n/30的现金折扣,对方商品已验收入库。双方均为增值税一般纳税人。要求:(1)设客户在10天内付款,作出公司的账务处理。
美国福克斯波罗公司当年为了生存急需新技术成果,一位工程师拿着新产品研制样品送给经理,总经理看到该产品的巧妙设计很惊喜,就在自己的抽屉东翻西找,最后终于找到了一只香蕉,满怀激情地对这位工程师说:“伙计,给你!”,这位工程师倍受感动。对员工进行激励的过程中
“中国共产党必须始终代表中国先进生产力的发展要求,代表中国先进文化的前进方向,代表中国最广大人民的根本利益。”这是对“三个代表”重要思想的集中概括。“三个代表”重要思想的根本出发点和落脚点是()。
下列有关法的原则的表述错误的是()。
Therearefewpeoplewhodrawuplifegoals.Mostpeoplewanttotakeonestepatatime,andarefrightenedwhentheyhavetos
最新回复
(
0
)