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
Although no one is certain why migration (迁移) of birds occurs, there are several theories. One theory is based upon the statemen
Although no one is certain why migration (迁移) of birds occurs, there are several theories. One theory is based upon the statemen
admin
2009-07-15
81
问题
Although no one is certain why migration (迁移) of birds occurs, there are several theories. One theory is based upon the statement that prehistoric birds of the northern hemisphere (半球队) were forced south during the Ice Age, when ice covered large parts of Europe, Asia, and North America. As the ice of rivers melted, the birds came back to their homelands, spent the summer, and then went south again as the ice advanced in winter. Once the migration became a habit, and now, although the glaciers (冰河) has disappeared, the habit continues.
Another theory proposes that the ancestral (祖先的) home of all modem birds was the tropics (热带). When the region became overpopulated, many different kinds of birds were crowded north. During the summer, there was plenty of food, but during the winter, short supply forced them to return to the tropics.
A more recent theory, known as photoperiodism (光照反应), suggests a relationship between increasing daylight and the feeling of certain glands (腺) in the birds’ bodies that may prepare them for migration. One scientist has been able to cause midwinter migrations by making birds uncovered to unusual periods of light. He has concluded that changes occur in the bodies of birds due to seasonal changes in the length of daylight.
选项
A、began migrating again
B、stopped migrating
C、continued migrating
D、migrated south and stayed there
答案
C
解析
第一段最后一句讲到迁移已经成为习惯,即使现在冰河不存在了,这个习惯却延续下来了。所以选[C]。
转载请注明原文地址:https://kaotiyun.com/show/GCyd777K
本试题收录于:
公共英语二级笔试题库公共英语(PETS)分类
0
公共英语二级笔试
公共英语(PETS)
相关试题推荐
Whatdoesthepassagemainlydiscuss?Whichofthefollowingstatementistrue?
Animationmeansmakingthingswhicharelifelesscomealiveandmove.Sinceearliesttimes,peoplehavealwaysbeenastonish
StudentsinStateUniversities______iftheirparentsliveinthatstate.Nearlyhalfofallcollegestudents______whilethe
—WhydoesSaraknowsomuchaboutAngkorWatt?—She______havebeenthere,orbecauseofsomeotherreasons.
Whichoffollowingisthebesttitleofthetext?
WhenEuropeansfirstcametoAfrica,theywereamazedtofindthatmanyAfricanshadmorethanonewife.Becauseofthispractic
TherearehundredsofTVchannels(频道)intheUnitedStates.Americansgetalotofentertainment(娱乐)andinformationfromTV.
WhatdidLindadoaftergraduatingfromcollege?
Whichofthefollowingstatementsisnottrueaccordingtoyourreading?Whichofthefollowingisthebesttitlefortheabove
Thereisnodenyingit:Boysthinkdifferentlyfromgirls.Eventhoughrecentbrainresearchevidenceiscontroversial(争议的),tha
随机试题
利用适当减小弯管模半径的方法,也可以有效地解决管子弯曲后的回弹。
合成血红蛋白的基本原料是
A.碘B.硒C.铜D.铁E.汞与血红蛋白沉着有关的是
该患牙应诊断为其治疗应选用
脾切除时应定期复查的项目是
在经济萧条时,降低利率能够刺激投资,防止经济下滑。( )
“四书”是封建社会科举取士的初级标准书。它所指的是哪四本书?()
关于新民主主义革命胜利的基本经验,下列表述错误的是()。
“千沟万壑,支离破碎”是用来形容我国的()。
什么是不注意视盲?它与注意捕获的区别是什么?
最新回复
(
0
)