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
Why don’t birds get lost on their long flights from one place to another? Scientists have puzzled over this question for many ye
Why don’t birds get lost on their long flights from one place to another? Scientists have puzzled over this question for many ye
admin
2009-05-28
72
问题
Why don’t birds get lost on their long flights from one place to another? Scientists have puzzled over this question for many years. Now they are beginning to fill in the blanks.
Not long ago, experiments showed that birds depend on the sun to guide them during day-flight hours. But what about birds that fly by night? Tests with man-made stars have proved that certain night-flying birds are able to follow the stars in their long-distance flights.
A dove spent its lifetime in a cage and had never flown under a natural sky. Yet it showed an inborn ability to use the stars for guidance. The bird’s cage was placed under a man-made star-filled sky. The bird tried to fly in the same direction as that taken by his outdoor cousins. Any change in the position of the make-believe stars caused a change in the direction of his flight.
Scientists think that doves, flying ill daylight, use the sun for guidance. But the stars are obviously their most important means of navigation (or flying). What do they do when the stars are hidden by clouds? Obviously, they find their way by such landmarks as mountains ranges, coastlines, and river courses. But when it is too dark to see these, the doves circle helplessly, unable to get their bearings.
选项
A、has been discovered recently
B、is known by everybody
C、still remains a mystery
D、has been known to scientists for years
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/pSwK777K
本试题收录于:
大学英语三级B级题库大学英语三级分类
0
大学英语三级B级
大学英语三级
相关试题推荐
Readthefollowingpassage.ChoosefromthesentencesA—Gtheonewhichbestfitseachgapof61—65.Therearetwoextrasenten
ItseemednormalwhenNguyenNgocTruongSonwantedtoplaychesswithhisparents.However,itwasunusualwhenherevealedtha
Dr.Smith,togetherwithhiswifeandtwosons,_____toarriveontheeveningflight.
Prisonsinthecountryareshortofstaff,;.meansprisonofficersareoverworkedandunderpaid.(SCET3:0912)
Howmenfirstlearnedtoinventwordsisunknown.Allwereallyknowisthatmen,unlikeanimals,somehowinventedcertainsound
Whydon’tbirdsgetlostontheirlongmigratory(迁徙)flight?Scientistshavepuzzledoverthisquestionformanyyears.Nowthe
Whydon’tbirdsgetlostontheirlongmigratory(迁徙)flight?Scientistshavepuzzledoverthisquestionformanyyears.Nowthe
Collegeisaplacetoexploremanypossibilities;youreallycan’tdoitall-unlessyoumanageyourtimewisely.Herearesomet
Thelinkbetweenhealthandincomeseemsprettyuncontroversial.【C1】______all,healthypeoplecanworklongerandharderthansi
A、Iworkhard.B、I’mdancing.C、I’vegotaheadache.D、Ilikeswimming.C问题为“你怎么啦?”四个选项中只有C“我头疼”是合适的回答。
随机试题
CCK刺激胰液分泌的特点是
术前患者常见的心理问题为()。
大剂量碘制剂不能单独长期用于治疗甲亢是因为
导致堕胎、小产的病因病机,除哪一项外,都为常见
《巴塞尔新资本协议》关于全面信息披露理念的表述,下面选项中不正确的是( )。
下列关于鼠标操作中各种指针的说法错误的是()。
《学记》中的“道而弗牵,强而弗抑,开而弗达”所阐明的教学原则是()
Wheredopesticidesfitintothepictureofenvironmentaldisease?Wehaveseenthattheynowpollutesoil,water,andfood,tha
A、Back-to-backcredit.B、Reciprocalcredit.C、Documentarycredit.D、Stand-bycredit.D单句问的是“为了确保履行协议而非真正付款的信用证称为什么信用证?”,答案应为stan
A、Helptheclientsre-evaluatetheirlives.B、Helptheclientsmakemoremoney.C、Helptheclientssucceedinlife.D、Helpthec
最新回复
(
0
)