题目内容

The research is so designed that once ________ nothing can be done to change it.

[　　]

A．begins
B．having begun
C．beginning
D．begun
答案：D
解析：

【巧解导析】非谓语动词作状语时注意它的逻辑主语必须与句子主语保持同一性(当然有时也有个别结构例外)，状语从句的简略形式也应注意这一问题．本小题once引导的状语从句强调人为因素，完整形式是once it is begun而不是once it begins，因此要用过去分词表被动．


提示：

【巧解点悟】非谓语动词实际上考查了多种因素如语态、时态等，在解题时一定要综合考虑，不然很容易出错．


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　　Sweet potatoes are fat-free,high in fiber and full of the vitamins that research suggests reduce your risk of life-shortening diseases．To stay healthy,we must eat more fruits and vegetables,and sweet potatoes are a great source of beta carotene（胡萝卜素）and other carotenoids．According to a study of the diets of almost 90,000 nurses,eating about one cup a day of fruils and vegetables rich in carotenoids(which the body turns into vitamin A)can cut your risk of stroke in halt and reduce your risk of heart disease by 22 percent．Other resear chsuggests beta carotene protects against breast,lung and stomach cancers．

　　Beta carotene is the most famous member of the carotenoids family．In fact,a medium sized sweet potato contains nearly 12 mg of beta carotene(antiaging experts usually suggest 6 to 11 mg perday)．Sweet potatoes are also a low-fat source of vitamin E．Research has linked high E diets with a lower risk of heart disease．This vitamin pill in an orange jacket also packs a vitamin C punch-it has more C than apricots(a kind of fruit)．Research suggests that vitamin C protects against ailments ranging from cataracts(an eye disease)to cancer．In addition,A UCLA(University of California,Los Angels)study linked high vitamin C diets with a longer life．Recent studies have showed that antioxidant vitamins C,E and beta carotene fight a fierce battle against free radicals（自由基）,which cause cell（细胞）damage and lead to various illnesses．Therefore,to keep fit,eat more sweet potatoes．

(1)

According to the text,there exists a lot of ________ in sweet potatoes．

[　　]

A．

fiber,beta carotene,other earotenoids,vitamin E and C

B．

beta carotene,other carotenoids,fiber,vitamin A and E

C．

vitamin A,beta carotene,fiber,vitamin E and C

D．

beta carotent,other carotenoids,vitamin A and E

(2)

This text as a whole suggests that eating sweet potatoes can help ________

[　　]

A．

cut your risk of stroke and heart disease

B．

protect against breast,lung and stomach cancers

C．

protect against ailments ranging from cataracts to cancer

D．

you stay healthy and reduce your risk of life shortening diseases

(3)

“This vitamin pill in an orange jacket”in the passage refers to ________

[　　]

A．

sweet potato

B．

vitamin C pill

C．

vitamin E pill

D．

beta carotene

(4)

The best title of this passage might be ________

[　　]

A．

The Vitamin Superstar

B．

On Sweet Potatoes

C．

Beta Carotene and Vitamins

D．

Diet and Disease

阅读理解： 　　

阅读下面短文，从所给四个选项中，选出最佳答案。

　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(柳树)attacked in the woods by caterpillars(毛毛虫)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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