Question

Why don’t birds get lost on their long migratory (遷移的) flights? Scientists tried their best to find the   1  to this question for many years. The reasons have been discovered only lately.
　　  2  ago experiments showed that birds depend on the sun to guide them   3  . But what about birds that fly mainly by night?  4  with man-made stars have   5  that certain night-flying birds are able to follow the   6  in their long distance flights.
　　One such   7  , a warbler (鳴禽), had spent its lifetime in a   8  and had never flown under a natural sky. Yet is showed its   9  by birth to use the stars for guidance. The bird's cage was put under a man-made star-filled sky at migration   10 . The bird tried to fly   11  the same direction as   12  taken by other birds in the building. Any 13 in the position of the make-believe (虛構(gòu)的) stars   14  a change in the direction of its flight.
　　Scientists think that warblers,  15 flying in daylight, use the sun for guidance. But stars are clearly their important   16  of navigation(導(dǎo)航). What do they do when the stars are   17  behind the clouds? Clearly, they find their way by such land   18  as mountains, coastlines and river courses. But when it's too   19  to see these, the warblers circle  201  , unable to find out where they were.
1. A. reply           B. answer      C. discovery      D. replies
2. A. Not long        B. Long       C. Centuries       D. Years
3. A. during the night                B. during daylight hours
C. in winter                     D. in the dark
4. A. Examinations    B. Labs       C. Tests           D. In the dark
5. A. been proved     B. found       C. been found      D. proved
6. A. stars           B. moon        C. route          D. sun
7. A. star            B. scientist      C. bird           D. flight
8. A. forest          B. cage         C. nest           D. cave
9. A. strength        B. ability        C. experience     D. practice
10. A. time          B. place         C. way          D. season
11. A. to            B. towards       C. in            D. under
12. A. that          B. which         C. one           D. it
13. A. one          B. change        C. way           D. bird
14. A. caused        B. gave          C. resulted        D. meant
15. A. for           B. when         C. after           D. they are
16. A. ways         B. means         C. objects        D. homes
17. A. shown        B. covered        C. moved         D. hidden
18. A. areas         B. surface         C. marks         D. signs
19. A. far           B. high           C. dark          D. bright
20. A. helplessly     B. quickly         C. easily         D. freely

Answer 1

1-5 BABCD 6-10 ACBBA 11-15 CABAB 16-20 BDCCA

1.   answer一般指經(jīng)過思考并有針對性的詳細(xì)解答；reply僅指一般的答復(fù)。
2.   not long ago對應(yīng)上段結(jié)尾的lately。
3.   下文“But...by night”提示此處與之相對而言。上文的sun也暗示了在白天。
4.   通過“測試”證明……
5.   當(dāng)prove意思是“證明或證實……的結(jié)果”時不用被動語態(tài)。
6.   見下段中間：“...use the stars for guidance”。
7.   warbler為鳥中的一類。
8.   下文第二句中有提示，本為“籠”中之鳥。
9.   利用星星導(dǎo)航是鳥類天生就有的一種“能力”。
10.   D為可數(shù)名詞，須有冠詞，且與空白前的at搭配不當(dāng)。
11.   朝……方向，用“in...direction”。
12.   that指代direction，后有?ed形式短語作定語。
13.   此句交代實驗中的重要環(huán)節(jié)，以證實warbler的“ability”。
14.    result要和in搭配。
15.   與后面動詞use所表示的動作“同時”。
16.   四個選項詞義相比，應(yīng)選means(手段)。
17.  云“遮”星，cover常與with連用。
18.   空白后as所接三個名詞(短語)均屬land marks(地面標(biāo)志)。
19.   空白前it指“天”，選dark。
20.    helplessly與下文unable相呼應(yīng)。