In Scotland, the number of wild salmon have been reduced because of uncontrolled deep-sea and coastal netting, by pollution, and by various other threats to the fish's habitat.
题目解答
历史版本-4 由cynsadore更新于2013-09-06 17:35:16
numbers可以指同类生物有很多
A,B,C都存在与非划线部分不平行。
D是不够简洁，adj.比定从更好。
所以选E. BY...,BY..., and BY...
题目释义：In Scotland，wild salmon's numbers have reduced by…by….and by…考点主谓一致（agreement） 平行结构（parallelism prediction） 逻辑意思（logical construction）
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the number of+复数名词，谓语用单数。
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and平行结构。
选项分析
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A. have错误，应该是单数。And后面跟了by，前后应对称的用reduced by。同时by pollution的承受者应该是wild salmon，所以the number of wild salmon错误。
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B. and平行错误同A。逻辑主语错误同A。
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C. the numbers错误。逻辑主语错误同A。and平行错误同A。
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D. that is not controlled不如uncontrolled简洁。
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E. correct。
补充说明Number的用法小结—by Mayanist：几种用法之间区别：非核心词与核心词；number的意义；number与相关成分的单复数一致关系。
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a number of / numbers of + 可数名词复数 + 动词复数
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可以理解为量词结构，a number of表示一些，numbers of表示大量
of后面的复数名词才是核心词，谓语动词因此总是复数
Many students arrived early, but only a number of them worked on their exercises.
The lake produces a good number of (=a lot of) salmon each season.
Numbers of birds fly across the lake.
另外：any number of 用于非正式场合，表示大量
There could be any number of (=many) reasons why she's late.
OG237. It seems likely that a number of astronomical phenomena, such as the formation of planetary nebulas, are caused by the interaction of two stars orbiting each other at close range.
OG152. When the technique known as gene-splicing was invented in the early 1970's, it was feared that scientists might inadvertently create an "Andromeda strain," a microbe never before seen on Earth that might escape from the laboratory and kill vast numbers of humans who would have no natural defenses against it.
709. The Coast Guard recently redesigned channel markers in the Chesapeake Bay to accommodate large numbers of ospreys, whose huge nests formerly obstructed the lights.
829. The speculative fever of the Roaring Twenties infected rich and poor alike; great numbers of people were dangerously overextended, credit was absurdly easy to obtain, and most brokerage houses required only ten percent cash for stocks bought on "margin."
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the number of + 可数名词复数 + 动词单数: number是核心词，可以被具体的一个数字表示 可数物品累积起来的数量, 可数名词需用复数形式。这时number是核心词，可以被具体化为一个数字，如50或者100，谓语动词因此总是单数
The number of students who participated the interview was 100.
Today's case brings the number of successful prosecutions in the region to thirty-four.
[这里有个疑问有待考证：是否可以从例子派生出The numbers of girl and boy students are respectively 30 and 70? 如果可以，则规则为：the number(s) of + n.(总是复数) + v.(单数或者复数-取决于number的形式)]。
