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
The cause of the decline of North Africa is popularly attributed to climatic changes, the theory being that the area became hott
The cause of the decline of North Africa is popularly attributed to climatic changes, the theory being that the area became hott
admin
2013-04-08
66
问题
The cause of the decline of North Africa is popularly attributed to climatic changes, the theory being that the area became hotter and drier and the people were forced to abandon a thriving civilization. However, some geologists, after carefully weighing the evidence, have challenged the conclusion that the climate has changed in any important way since Roman times. Although climatological factors may also have contributed, it was man who destroyed the balance of nature responsible for maintaining soil fertility and moisture.
Why is it that under certain circumstances, the plant cover is unable to regenerate itself, thus setting the stage for serious erosion (腐蚀)? To answer this question, let us take an extreme example, the destruction of tropical rain forests. In general, the equatorial (赤道附近的) soil is poor: forests can exist in these regions only because they are part of a balanced cycle. All that the forest produces is returned to the forest. The organic matter that falls from the trees constitutes the humus (腐殖土) that the forest requires. When people cut down all the trees to make room for crops, the soil is laid bare and, deprived of shade, heats up. An increase in soil temperature increases the rate of decomposition (分解) of organic matter. Organic nitrogen (氮) is converted into soluble ammonia (氨) and nitrates (硝酸盐), which the rains quickly leach (沥滤,溶滤)away. It has been calculated that a rise in temperature from 77 to 78.8 may increase the loss of nitrogen by fifteen to twenty pounds per acre per year. With the fertility of soil destroyed, an irreversible change from forest to desert can be initiated.
What do people usually think contributed to the decline of North Africa?
选项
A、Human factors.
B、Economic factors.
C、Climatic factors.
D、Population factors.
答案
C
解析
题目询问人们通常认为是什么原因导致了北非的衰落。这是对第1句的改写。故选项C正确。
转载请注明原文地址:https://kaotiyun.com/show/Ayr7777K
0
大学英语四级
相关试题推荐
Tounderstandthemarketingconcept,itisonlynecessarytounderstandthedifferencebetweenmarketingandselling.Nottooma
Inmyopinion,playingvideogamesnotonlytakesmuchtimebutis____________(也有害健康).
Whatisthepassagemainlyabout?WhichofthefollowingstatementsisNOTcorrect?
A、Theprojectdemandsmoretime.B、Theprojectisonlyhalfdone.C、Shewillfinishitwithinfourmonths.D、Shehasspentless
A、English.B、Biology.C、IntroductiontoEnglishLiterature.D、Arequiredcourse.C细节题。四个选项的内容在录音中都有提及,关键是听清题目问的是男士和女士一起学的是什么课。回
A、Tobeanarchitect.B、Togointothebusiness.C、Tobemoreinteresting.D、Tobecomeanartist.AW:Ireallywishoursonwoul
CrippledbyComputersbyJaniceM.Horowitz
A、Lendherhishikingshoes.B、Bemoreflexible.C、Lendherhisgymshoes.D、Takemoreexercise.D对话中男士问女士他应不应该加入徒步旅行者团队,女士回答Why
Anti-FascistWarinthe1930sand1940sTheantiFascistwarbetweenthe1930sand1940swasthefirstjustwarofaglobal
Mr.Blairhascomeinthe______ofalegaladviser.
随机试题
藿香与佩兰均有的功效是()
神经系统中药中毒反应的表现有()。
根据《招标投标法》要求,必须以招标方式进行工程项目建设及与建设有关的设备、材料等采购总体范畴包括( )。
企业财务部门为了日常零星开支的需要,预付给企业内部各单位和职工个人备用的款项是()。
某企业固定资产为800万元,永久性流动资产为200万元,波动性流动资产为200万元。已知长期负债、自发性负债和权益资本可提供的资金为900万元,则该企业采取的是()。
在田径教学中,学生学习动作技能要经历一个由不会到会,由泛化到分化,再到()的发展过程。
2007年全国大中型工业企业的销售额约为()。全国设有科技机构的企业的数量的变化趋势是()。
张某为给病危的父亲治病急需用款10万元,王某表示愿意借给张某,但一年后须加倍偿还,否则须以张某某三居室住房代偿,张某表示同意。此行为属于()。
2006年1月26日,甲公司销售一批材料给乙公司,含税价105000元,款项尚未收到。2006年7月1日,乙公司发生财务困难,经双方协议,甲公司同意乙公司用产品抵偿债务。该产品市价为80000元,增值税税率为17%,产品成本为70000元。甲公司为该
Thesymbolsofmathematics______wearemostfamiliararethesignsofaddition,subtraction,multiplication,divisionaridequ
最新回复
(
0
)