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 ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologist
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologist
admin
2013-04-22
32
问题
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologists long regarded it as an example of【C1】______ by natural selection, but for physicists it bordered on the miraculous. Newton’s laws of motion【C2】______ that the total amount of spin of a body cannot change【C3】______ an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external torque, it ought not to be able to【C4】______ as it falls. In the speed of its execution, the【C5】______ of a tumbling cat resembles a magician’s trick. The gyrations of the cat in midair are【C6】______ fast for the human eye to follow, so the process is obscured. 【C7】______ the eye must be speeded up, or the cat’s fall slowed down for the phenomenon to be observed. A century ago the former was accomplished 【C8】______ high-speed photography using equipment now【C9】______ in any pharmacy. But in the nineteenth century the 【C10】______ on film of a falling cat constituted ascientific experiment. The experiment was described in a paper presented to the Paris Academy in 1894. Two sequences of twenty photographs【C11】______ , one from the side and one from behind,【C12】______ a white cat in the act of righting itself. Grainy and quaint【C13】______ they are, the photos show that the cat was dropped upside down, with no initial spin, and still landed on its feet. Careful analysis of the photos reveals the secret. As the cat rotates the front of its body【C14】______ , the rear and tail twist counterclockwise,【C15】______ the total spin remains zero,【C16】______ Newton’s laws. Halfway down, the cat pulls in its legs before reversing its twist and them extends them again,【C17】______ the desired end result. The explanation was that while no body can acquire spin without torque, a flexible one can readily change its【C18】______ . Cats know this instinctively, but scientists could not be sure how it happened【C19】______ they increased the speed of their【C20】______ a thousand fold.
【C3】
选项
A、unless
B、until
C、when
D、after
答案
A
解析
根据句型结构和逻辑关系的分析,答案是A。
转载请注明原文地址:https://kaotiyun.com/show/jEQK777K
0
专业英语四级
相关试题推荐
Itisnoteasytopin-pointthe【C1】______oftheChristmasfeast,todaythemostimportantfeastoftheChristmasseasoninmost
Seventy-four-year-oldsarethemost【C1】______peopleinthepopulation,accordingtoanewresearch.Fewerresponsibilities,fina
Seventy-four-year-oldsarethemost【C1】______peopleinthepopulation,accordingtoanewresearch.Fewerresponsibilities,fina
Whatdoyoulookforinapotentialdate?Sincerity?Goodlooks?Character?Conversationalability?Askedto【C1】______suchquali
Welearnfromthepassagethatabouttwo-thirdsofthecoursesaretaughtthrough______.
Decidewhichofthechoicesgivenbelowwouldbestcompletethepassageifinsertedinthecorrespondingblanks.Mostworthw
Openupmostfashionmagazinesandyouwillseeincrediblythinmodelswithimpossiblehairandwearingunreasonablyexpensive,
Togiveyouageneralideaofourproducts,weenclosethecataloguesshowingvariousproductshandledbyuswithdetailedandm
Advertisingmedialikedirectmail,radio,televisionandnewspapers______toincreasethesalesofindustrialproducts.
Whichisnotmentionedinthepassageasanaspectthatfarmingactivitiesaredamaging?
随机试题
国际市场营销比国内市场营销难度更大,表现在()
枕左前位胎头进入骨盆时,衔接的径线是
有关牙本质小管的结构,以下哪项是错误的
根据《土壤污染防治行动计划》开展污染治理与修复,改善区域土壤环境质量的要求,下列说法中,错误的是()。
下列有关资产、负债计税基础的表述中不符合企业会计准则规定的是()。
对实行物业承接查验制度的说法,错误的是()。
《公益事业捐赠法》对捐赠财产用途的规定包括( )。
人的本质在其现实性上,是一切社会关系的总和。社会中的人,生来就处在复杂的关系网中,而社会关系中最基本的关系是
Paris:ThankstoaFrenchinsurancecompany,bridesandbridegroomswithcoldfeetnolongerfacefinancialdisasterfromacanc
"Ithurtsmemorethanyou",and"Thisisforyourowngood."Thesearethe【C1】______mymotherusedtomakeyearsagowhenIhad
最新回复
(
0
)