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 fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries,
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries,
admin
2010-07-06
28
问题
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries, How such large creatures, which weighed in some eases as much as a piloted hang-glider and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures were — reptiles or birds — are among the questions scientists have puzzled over.
Perhaps the least controversial assertion about the pterosaurs is that they were reptiles. Their skulls, pelvises, and hind feet are reptilian. The anatomy of their wings suggests that they did not evolve into the class of birds. In pterosaurs a greatly elongated fourth finger of each forelimb supported a wing like membrane. The other fingers were short and reptilian, with sharp claws. In birds the second finger is the principal strut of the wing, which consists primarily of feathers. If the pterosaurs walked on ail fours, the three short fingers may have been employed for grasping. When a pterosaur walked or remained stationary, the fourth finger. and with it the wing, could only turn upward in an extended inverted V-shape along each side of the animal’s body.
The pterosaurs resembled both birds and hats in their overall structure and proportions. This is not surprising because the design of any flying vertebrate is subject to aerodynamic constraints. Both the pterosaurs and the birds have hollow bones, a feature that represents a savings in weight. In the birds, however, these bones are reinforced more massively by internal struts.
Although scales typically cover reptiles, the pterosaurs probably had hairy coats. T.H. Huxley reasoned that flying vertebrates must have been warm-blooded because flying implies a high rate of metabolism, which in turn implies a high internal temperature. Huxley speculated that a coat of hair would insulate against loss of body heat and might streamline the body to reduce drag in flight. The recent discovery of a pterosaur specimen covered in long, dense, and relatively thick hair—like fossil material was the first clear evidence that his reasoning was correct.
Efforts to explain how the pterosaurs became airborne have led to suggestions that they launched them- selves by jumping from cliffs, by dropping from trees or even by rising into light winds from the surfaces of waves Each hypothesis has its difficulties. The first wrongly assumes that the pterosaurs’ hind feet resembled a hat’s and could serve as hooks by which the animal could hang in preparation for flight. The second hypothesis seems unlikely because large pterosaurs could not have landed in trees without damaging their wings. The third calls for high waves to channel updrafts. The wind that made such waves however, might have been too strong for the pterosaurs to control their flight once airborne.
The author views the idea that the pterosaurs became airborne by rising into light winds created by waves as ______.
选项
A、revolutionary
B、unlikely
C、unassailable
D、probable
答案
B
解析
分析推理题。文章第五段在提出几种解释后,用Each hypothesis has its difficulties一句对这些假说都进行了否定,并且在该段后面几句分析了否定的原因,因此答案是B 。
转载请注明原文地址:https://jikaoti.com/ti/YpisFFFM
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
Fromthecontext,weknowthat"attributes"(Para.1)meansWhichofthefollowingdoesNOTpresentatruepictureofAmerican
Itcanbeinferredfromthepassagethatscientistsnowgenerallyagreethatthe______.TheideasattributedtoT.H.Huxleyi
Themainpurposeofthefirstparagraphis______.WhatdidthefuturelooklikeforBritain’sfoodproductionatthetimeofw
WhatarethetwoseasoningsusedbymostAmericans?
Helandedinthiscountrywhenhewas4yearsoldwithoutawordofEnglish,andtherehehasrecentlygraduatedwithhonorsfro
Predictionsofmanyrobotsinindustryhaveyetcometrue.Fortenyearsormore,manufacturersofbigrobotshaveexplainedhow
Predictionsofmanyrobotsinindustryhaveyetcometrue.Fortenyearsormore,manufacturersofbigrobotshaveexplainedhow
Allthewisdomoftheages,allthestoriesthathavedelightedmankindforcenturies,areeasilyandcheaply【21】______toal
Allthewisdomoftheages,allthestoriesthathavedelightedmankindforcenturies,areeasilyandcheaply【21】______toal
Allthewisdomoftheages,allthestoriesthathavedelightedmankindforcenturies,areeasilyandcheaply【21】______toal
随机试题
在Na2CO3水溶液中,加入下列物质,能起反应且看不出现象的是()。
下述哪一部位不是淋病的好发部位
绘制双代号网络图的步骤包括()。
水泥混合料铺筑前,应对()等设施项目进行检查。
抗震设防在()时,蓄电池组必须用钢抗震框架或柜架安装。
张某与李某同住一省,张某居住在B县,李某居住在C县。张某因侵权责任对李某提起民事诉讼,应由( )管辖。
首个总部落户于中国北京的国际性旅游组织是()。
Datahasahabitofspreading.ItslipspastmilitarysecurityanditcanalsoleakfromWikiLeaks.Itevenslippedpasttheban
下列Applet实现了在Applet窗口中绘制一个以(70,70)为圆心,50为半径,边框为绿色的圆,圆心是红色的。选择正确的语句填入下面横线处。importjava.awt.*;importjava.applet.*;
Itisnoteasytoremaintranquilwheneventssuddenlychangeyourlife.
最新回复
(
0
)