一道SAT语法题！！！

Question

Twice as many bird species inhabit Ecuador as inhabit North America.
这里为何要用as inhabit ?

Answer 1

Twice as many bird species inhabit Ecuador as inhabit North America.
= Twice as many bird species inhabit Ecuador as (those that) inhabit North America.
省略连词，平行结构。

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those that是指示代词和关系代词吧！
用as......as表示一样多或几倍有多种方式，具体怎麽用？

追答

一、as…as 结构的基本用法
　　其基本意思为“与……一样”，其中的第一个as副词，其后通常接形容词或副词(用原级)，第二个as可用作介词(后接名词或代词)或连词(后接从句)。使用时应注意以下几点：
　　1. 在否定句中，第一个 as 也可换成 so：
　　He doesn’t study as [so] hard as his brother. 他学习不如他弟弟努力。
　　2. 在该结构的两个as之间通常接形容词或副词的原级，但若涉及数量或程度，可用“as much+不可数名词+as”和“as many+可数名词复数+as”：
　　You’ve made as many mistakes as I have. 你犯的错误和我犯的一样多。
　　I haven’t got as much money as I thought. 我不像原来想像的有那么多钱。(R2/92)
　　其间接形容词时，有时该形容词还可修饰另一名词，但这个名词应带有不定冠词(注意词序)：
　　She is as good a cook as her mother. 她和她妈妈一样是位好厨师。
　　也可说：She is a cook as good as her mother.
　　但不说：She is as a good cook as her mother. 或They are as good cooks as us.
二、关于第二个as的词性
　　第二个as后接从句时，该as通常为连词，但有时这个as还充当其后从句的主语或宾语，此时该as实为关系代词。如：
　　I gave him as much as he could eat. 他能吃多少，我就给了他多少。
　　We’ve got food for as many people as want it. 我们的食物，无论多少人吃都够了。
　　注：若第二个as用作连词引导一个表示将来意义的从句，则该从句可用现在时表示将来，也可直接使用将来时态。如：
　　We’ll get there as soon as you do [will]. 你一到，我们就到。
三、as…as…结构的修饰语
　　该结构根据情况可用使用以下修饰语：(not) nearly, almost, just, nothing like, exactly, not quite, half, one-ten, twice, three times, 30 per cent等，并且这些修饰语必须置于第一个as之前，而不能置于其后。如：
　　He doesn’t play half as well as his sister. 他演奏的水平不及他姐姐的一半。
　　This dress is twice as expensive as that. 这件连衣裙比那件贵一倍。
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继续

追答

（续）
四、as…as…结构的省略
　　在非正式场合(尤其是美国英语中)，有时可以省略第一个as。如：
　　When over forty, he married a woman poor as himself. 他在40多岁时娶了一个像他本人一样穷的女人。
　　另外，若意思明确，有时可省略第二个as及其后的相关词语。如：
　　The pianos in that shop will be cheaper, but not as good. 那家商店的收音机会便宜些，但质量没那么好。

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本句 Twice as many bird species inhabit Ecuador as inhabit North America.
many bird species inhabit Ecuador 许多种类的鸟类以Ecu...厄瓜多尔为栖息地。
many bird species inhabit North America, too. 同样有许多种类的鸟类以北美洲为栖息地。

Many 是这里的形容词，多。是个可数名词的形容词，可数就可以清楚地比较多少。
因此，厄瓜多尔不属于北美洲。但是只凭这两句还不知道两地栖息的鸟类种类哪个地方比较多

然后，
Twice as many bird species inhabit Ecuador as (~~the many bird species which) inhabit North America. 把厄瓜多尔的情况和北美洲的情况比，比较结果是前者被Twice修饰了，如果后者是一，前者就是二。
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用代词代替 Twice as many bird species inhabit Ecuador as (~~those which) inhabit North America.
-->
Twice as many bird species inhabit Ecuador as () inhabit North America.

你说得对确实是代词和指示词被省略了。
平行法则是指 寻找被省略的内容到底是对应前文什么内容。

就变成您给出的句子了。

翻译是:以Ecu...厄瓜多尔为栖息地的鸟类的种类数是以北美洲为栖息地的两倍。

欢迎追问！并望采纳。

Answer 2

这是个as as引导的比较结构，是把在两个鸟类栖地的数量相比较。

Answer 3

理解错误了，这里其实是一个as......as 的结构；
这句子：厄瓜多尔定居的鸟是北美的2倍

Answer 4

前后比较，结构要并列，比如I am as tall as you are. 一定要有are 机构才完整