天山-7-41

cookercai

83.
The number of plant and animal species that humans are known to have forced to extinction in the last half millennium is over 800.
(A) humans are known to have forced to extinction
(B) humans are known as having forced to become extinct
(C) humans are known for forcing to become extinct
(D) are known that humans forced to become extinct
(E) are known as having been forced to extinction by humans
A. 正确，完成时态突出了“已经”灭绝的含义。
B. Be known as用于此处语义不正确
C. Be known for用于此处语义不正确
D. That are known that… 表达笨拙
E. Be known as用于此处语义不正确；having been forced表达笨拙
句子结构：The number of… is over 800. 为句子主结构。
划线部分为句子限定性定语从句，修饰species，表示人们知道的已经绝种的动物和植物的数量为800种。在定语从句中，that指代plant and animal species，做从句have forced的宾语，而不是从句主语。从句还原之后正常语序形式为：humans are known to have force that (指代plant and animal species) to extinction….
句子结构（Grammatical Construction）, 习惯用语（Idiom）
1) that指代species在定语从句中作known的宾语
2) be known to do something为正确的习语，Be known as…作为…而著名，know for…表示以…而著名，或而被别人认知。

sch

以下是引用ring_cheng在2005-5-6 14:20:00的发言：

谢谢anyname, 同意此题选C，但对anyname的解释有不尽相同的看法，就A/B而言：

A. when it is known that humans made

B. at which it is known that humans had made

这里还有一个主要问题：A/B都没有指明when/at which是修饰从句中的it is known（知道“人类用石器”的时间）还是humans (had) made（人类用石器的时间）. 属修饰歧义错误。

本来选A，仔细考虑后改支持C。做题时看不惯at which，稍微查了一下，the date when....和the date at which都行。大家都同意答案在A和C间产生，简化后比较一下：

A：(This finding) pushes back by X years the earliest date when it is known that humans made tools

C： (This finding) pushes back by X years the earliest date at which humans are known to have made tools.

1. A最大的问题是歧义。when... 本应作定语，但也是个完美的状语从句，意思就变成：当知道人类造工具这件事情的时候，this finding pushes back....。同一个东西可能作两种成分，并导致两个不同的意思，这种表达方式在GMAT中是禁止的。B 就没这个问题，因为at which...只能作定语从句，不能作状语。

2. be known to have done sth的问题。我觉得，当be known 和 do sth的发生的时间一致时，用be known to do sth；而do sth发生在be known之前时，则要用be known to have done sth。这里的情形显然属于后者。

所以选C

附known to do sth的例句：

1. 大全748：...few people are known to have recovered from the disease once the clinical symptoms have appeared.

2. 大全849：...few people have been known to taste it for the first time without requesting more.

3. og49：......satellites now known to orbit the distant planet.

请问蓝色部分的字体:

这部分说得有道理.做题时候我也想到,但是我的问题是,您说的这个情况,是不是也同样适用于C呢?

C: at which humans are known to have made

at which 修饰"humans被知道(用石器)"的时间 (are known to have made),而不是修饰人类"用石器"的时间.

简而言之,C中的 at which为啥就不能修饰 are known这个动词了? at which 为啥就一定要修饰 to have made 这动词了呢??

这点上我认为ABC没有区别啊?谁能说说?

jonath

我觉得有时候并正确选项并不一定毫无瑕疵，只是它相比其它选项来说是最优选择。

这也是ETS惯用伎俩中的一招。

xiaoda

up

winniebxf

agree on C
though I chose A at first

夜凉如水

when 确实不如at which意思更为准确，同时句子开端有have dated这里用have known也不算突兀。 E的话 句子重心都改变了 还是支持C

bongrim

Thank you very muc!!!

岳如初

以下是引用gonghao在2007-7-11 9:46:00的发言：

对于A的解释用定从和状从来排除有点一竿子打死一船人的情况

如果如大家所说那对于when引导的定语从句是不是都会有状语从句的歧义呢？

这样说了when在GMAT里的使用那真是如履薄冰了

个人理解：

A when本身没有错，可能只是错在it is know that 这个ETS不喜欢的结构，因为it的指代歧义存在。

C ETS更加喜欢，know to这样的结构

但是对于C里的have done后接明显的过去时标志，这样的使用确有不妥之处

anyway，C 里的at which 即使换成when 也依然是答案

大家只有记住，看到 it is know that和know to并存的时候长个心眼了

之前众说纷纭的觉得有点乱，这个非常清楚！！

aeoluseros

以下是引用sch在2008-2-18 1:08:00的发言：

请问蓝色部分的字体:

这部分说得有道理.做题时候我也想到,但是我的问题是,您说的这个情况,是不是也同样适用于C呢?

C: at which humans are known to have made

at which 修饰"humans被知道(用石器)"的时间 (are known to have made),而不是修饰人类"用石器"的时间.

简而言之,C中的 at which为啥就不能修饰 are known这个动词了? at which 为啥就一定要修饰 to have made 这动词了呢??

这点上我认为ABC没有区别啊?谁能说说?

同问...

aeoluseros

还是不明白A里面the date when it is known that humans made  stone tools.里面，when会不会被认为修饰it is known？而不是修饰made?

以及C里面 the earliest date at which humans are known to have made  stone tools.这个at which会不会被认为修饰are known而不是修饰have made stone tools？