Most birds find it safe to sleep in the trees, but __________ they have eggs or young chicks, they don’t use a nest.

A. why   B. how   C. unless    D. where

C。


解析:

將四個選項的意思分別套入句中，只有填unlessunless時意思最通順。為便于理解，句子也可轉(zhuǎn)換成：Most birds find it safe to sleep in the trees, but they don’t use a nest unless they have eggs or young chicks.

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Most birds find it safe to sleep in the trees,but_______they have eggs or young chicks,they don’t use a nest.

A.why                                                             B.how

C.unless                                                          D.where

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科目：高中英語 來源： 題型：

.Most birds find it safe to sleep in the trees, but __________ they have eggs or young chicks, they don’t use a nest.

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完形填空（共20小題；每小題1分，滿分20分）
請認真閱讀下面短文，從短文后各題所給的A、B、C、D四個選項中，選出最佳選項，并在答題卡上將該項涂黑。
Most people think of birds as feathered animals that fly. Scientists,   36 , do not define (給…下定義) birds as animals that fly, because some birds do not. Of the 10,000 or so species of birds, 46 cannot   37 . Flight plays a key role in   38  for most birds. It allows them to find food over a   39  area and to get away from enemies. Ancestors of flightless birds may have   40   their ability to fly because they had no regular predators (捕食者) or did not need to fly to find food. Rather than fly, some of these birds developed other   41  to catch food and avoid enemies. Two examples of   42  birds are penguins and ostriches.
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【小題1】
A．thusB．howeverC．thereforeD．otherwise
【小題2】
A．standB．flyC．hearD．sing
【小題3】
A．growthB．communicationC．healthD．survival
【小題4】
A．wideB．familiarC．crowdedD．special
【小題5】
A．developedB．improvedC．lostD．proved
【小題6】
A．partsB．habitsC．waysD．tools
【小題7】
A．wildB．interestingC．rareD．flightless
【小題8】
A．Instead ofB．Because ofC．BesidesD．Unlike
【小題9】
A．quicklyB．carefullyC．differentlyD．gradually
【小題10】
A．shapeB．color C．bone D．skin
【小題11】
A．ifB．a(chǎn)ndC．butD．so
【小題12】
A．helpB．feedC．protectD．hide
【小題13】
A．killB．noticeC．confuseD．frighten
【小題14】
A．dawnB．darknessC．dangerD．food
【小題15】
A．lookB．escapeC．moveD．fight
【小題16】
A．successfulB．naturalC．unusualD．positive
【小題17】
A．realizedB．a(chǎn)ctedC．stoppedD．a(chǎn)rrived
【小題18】
A．broughtB．foundC．boughtD．hunted
【小題19】
A．providedB．formedC．destroyedD．controlled
【小題20】
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