.Some researchers believe that there is no doubt ____ a cure for AIDS will be found.

       A. which.   B. whether    C. what    D. that.

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　Can trees talk? Yes——but not in words． Scientists have reason to believe that trees do communicate (互通信息) with each other． Not long ago, resear- chers learned some surprising things． First a willow tree(柳樹(shù))attacked in the woods by caterpillars(毛毛蟲(chóng))changed the chemistry of its leaves and made them taste so terrible that the caterpillars got tired of the leaves and stopped eating them． Then even more astonishing, the tree sent out a special vapour — a signal causing its neighbours to change the chemistry of their own leaves and make them less tasty．

　　　Communication, of course, doesn't need to be always in words． We can talk to each other by smiling, raising our shoulders and moving our hands． We know that birds and animals use a whole vocabulary of songs, sounds, and movements． Bees dance their signals, flying in certain patterns that tell other bees where to find nectar(花蜜)for honey． So why shouldn't trees have ways of sending messages?

1． When attacked, a willow tree will protect itself by________．

[　　]

A． changing its leaves’chemistry

B． changing its leaves’colour

C． talking to caterpillars

D． sending a special vapour

2． From the passage we know that catrpillars________．

[　　]

A． like willow trees

B． enjoy eating fallen leaves

C． feed on willow tree leaves

D． could communicate with willow trees

3． Caterpillars will stop eating willow tree leaves which________．

[　　]

A． have a chemical change and become tasteless

B． have a pleasant taste

C． are being attacked

D． are communicating

4． According to the passage, how do willow trees communicate with each other?

[　　]

A． They talk in words．

B． They send out a special vapour．

C． They wave their leaves．

D． They make special sounds．

5． According to the passage, bees communicate with each other by______．

[　　]

A． talking

B． making unusual sounds

C． singing songs

D． fly in certain patterns

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