首页
登录
职称英语
A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely
A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely
游客
2025-04-27
13
管理
问题
A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely land--that is the image most people have of deserts. But how true is this picture? Deserts are drylands where rainfall is low. This is not to say rain never falls in deserts. It may fall once or twice a year in a fierce torrent that fades almost as soon as it has begun, or which evaporates in the hot air long before it has got anywhere near the earth. It may fall in a sudden sweeping flood that carries everything in its path. Rains may only come once in five or six years or not fall for a decade or more. The Mojave desert in the United States remained dry for twenty-five years.
Without water no living thing can survive, and one feature of the desert landscape is the absence of vegetation. With little rain and hardly any vegetation the land suffers under the sun. There are virtually no clouds or trees to protect the earth’s surface and it can be burning hot. Under the sun, soils break up and crack. Wind and torrential rain sweep away and erode the surface further. Eight million square kilometers of the world’s land surface is desert. Throughout history deserts have been expanding and retreating again. Cave paintings show that parts of the Sahara Desert were green and fertile about 10, 000 years ago, and even animals like elephants and giraffes roamed the land. Fossil and dunes found in fertile and damp parts of the world show that these areas were once deserts. But now the creation of new desert areas is happening on a colossal scale. Twenty million square kilometers, an area twice the size of Canada, is at a high to very high risk of becoming desert. With a further 1.25 million square kilometers under moderate risk, an area covering 30% of the earth’s land surface is desert, becoming desert, or in danger of becoming desert. The rate of growth of deserts is alarming. The world’s drylands which are under threat include some of the most important stock-rearing and wheat-growing areas and are the homes of 600 - 700 million people. These regions are becoming deserts at the rate of more than 58, 000 square kilometers a year or 44 hectares a minute. In North Africa at least 100, 000 hectares of cropland are lost each year. At this rate there is a high risk that we will be confined to living on only 50% of this planet’s land surface within one more century unless we are able to do something about it. [br] How much of the world’s land surface is at risk of becoming desert?
选项
A、Less than ten million square kilometers.
B、Twenty million square kilometers.
C、More than twenty million square kilometers.
D、30% of the world’s land surface.
答案
C
解析
转载请注明原文地址:http://tihaiku.com/zcyy/4055666.html
相关试题推荐
Ascorchingsun,anendlessseaofsandandawaterless,forbiddinglylonely
Ascorchingsun,anendlessseaofsandandawaterless,forbiddinglylonely
Telephonessavethefeetandendlessamountsoftime.Thisisduepartlytothe
Inspiteof"endlesstalkofdifference",Americansocietyisanamazingmac
Inspiteof"endlesstalkofdifference",Americansocietyisanamazingmac
Inspiteof"endlesstalkofdifference",Americansocietyisanamazingmac
Theworstthingyoucandoiskeepyourselfinanendlesscycleofrelations
Theworstthingyoucandoiskeepyourselfinanendlesscycleofrelations
Theworstthingyoucandoiskeepyourselfinanendlesscycleofrelations
Inspiteof"endlesstalkofdifference",Americansocietyisanamazingmach
随机试题
Itisverydifficulttosayjustwhencolonizationbegan.Thefirsthundred
WhenIwasachildIhadviolinlessonsforsixorsevenyears.Musicgavem
喉结核的感染途径包括:A.血行播散途径 B.直接接触 C.种植方式 D.淋
高应变法不适用于H型钢桩。()
现今仍流行男不娶、女不嫁的“阿注”婚的民族是( )。A.畲族 B.白族 C
我国保险的基本原理有( )。 Ⅰ.大数法则 Ⅱ.风险选择原则 Ⅲ.风险分
下列城市总体规划成果内容,应与省域城镇体系规划衔接的有( )。A.城市社会经济
期货从业人员在进行投资分析或者提出投资建议时,应当勤勉尽责、(),投资分析及投
关于推土机提高推土生产率的方法,不正确的是()。A.槽形推土 B.下坡推土
某人因有机磷农药中毒,致使神经纤维末梢释放的乙酰胆碱不能失活而作用加强。患者不会
最新回复
(
0
)