首页
登录
职称英语
The cause of the decline of North Africa is popularly attributed to climatic
The cause of the decline of North Africa is popularly attributed to climatic
游客
2024-02-23
6
管理
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 tithes. 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. [br] Increase in the temperature of tropical soil ______.
选项
A、might cause the overflow of flood
B、may lead to the loss of organic nitrogen in it
C、will produce a great deal of organic nitrogen
D、is harmless to the growth of rain forests
答案
B
解析
这三句话表明温度升高会导致大量有机氮的流失。选项B符合原文意思。
转载请注明原文地址:https://www.tihaiku.com/zcyy/3474736.html
相关试题推荐
Theminister___________(拒绝回答关于)therumorsofhisresignation.declinedtocom
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Someobservershaveattributedthedramaticgrowthintemporaryemploymentt
Someobservershaveattributedthedramaticgrowthintemporaryemploymentt
[originaltext]CamerooninWestAfricaisanationof24separatelanguages
随机试题
Conventionalwisdomhasitthatmalebirdsareloyalandfaithfulbecauseth
下列灭菌方法不属于湿热灭菌法的是A.热压灭菌法B.流通蒸气灭菌法C.煮沸灭菌法D
下列属于经纪活动特点的有()。(2006年真题)A.活动内容的服务性 B.
Shelikestovisitexoticislands.A:dist
国家向丧失劳动能力,失去就业机会以及遇到其他事故而面临经济困难的公民提供的基本生
期货合约最小变动价位的设置是为了保证市场有适度的流动性,所以最小变动价位越小越好
(2012年)下列促销方式中,属于营业推广的有()。A.客户经理上门推销新业务
下列关于有企业所得税情况下的MM理论的说法中,正确的有()。A.高杠杆企业的债
下列使用注册商标的情形中,应当承担行政责任的是( )。A.自行改变注册商标的
取得安全生产许可证必须具备的条件有( )。A.特种作业人员经考核合格 B.职
最新回复
(
0
)