天山-7-41

dingding111

支持anyname, 特别是第一个解释完全体现了OG的宗旨。补充第二个解释 “ to have made tools ”应该是表明一种状态吧。

ring_cheng

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.

BiteGmat

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。

太精彩了！鼓掌！

bobobear

同意ringcheng的解释。茅塞顿开啊！

ring_cheng

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。

请注意：A选项中的push是用分词，不可以转成独立的句子：

pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools. 不可变成：

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

因为如果when是状语从句的话，需要跟独立句子而不能跟分词。

anyname

以下是引用ringcheng在2005-5-20 12:04:00的发言：
>

请注意：A选项中的push是用分词，不可以转成独立的句子：

pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools. 不可变成：

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

因为如果when是状语从句的话，需要跟独立句子而不能跟分词。

"因为如果when是状语从句的话，需要跟独立句子而不能跟分词"? 不准确吧？看看OG159:

Five fledgling sea eagles left their nests in western Scotland this summer, bringing to 34 the number of wild birds successfully raised since transplants from Norway began in 1975.

raised也是分词。还有OG4：...to have it quickly processed into juice concentrate before warmer weather returns and rots the fruit. OG1 AB中的occurring when，没有说错在when...不能跟分词吧。

p.s.: 我上CD网速非常慢，不知为何？以前挺快的。。。

[此贴子已经被作者于2005-5-25 14:00:29编辑过]

diehard

自己选的A，现在觉得C更好一些

大家的论述都很精彩

我想补充一下C选项的现在完成时的问题

用现在完成时是想表明在那一个时间点之前，都存在的情况。

也就是说

在XXXX年前，人们已经开始使用石器了

drunkbear

anyname解释得太精彩了,茅塞顿开啊

ring_cheng

以下是引用anyname在2005-5-25 13:51:00的发言：

"因为如果when是状语从句的话，需要跟独立句子而不能跟分词"? 不准确吧？看看OG159:

Five fledgling sea eagles left their nests in western Scotland this summer, bringing to 34 the number of wild birds successfully raised since transplants from Norway began in 1975.

raised也是分词。还有OG4：...to have it quickly processed into juice concentrate before warmer weather returns and rots the fruit. OG1 AB中的occurring when，没有说错在when...不能跟分词吧。

p.s.: 我上CD网速非常慢，不知为何？以前挺快的。。。

确实，我还没有找到在ING后面一定不可以接从句的例子，在OG205中另有一例说明副词从句只能接有完整的句子而不能接介词结构：

205. The peaks of a mountain range, acting like rocks in a streambed, produce ripples in the air flowing over them; the resulting flow pattern, with crests and troughs that remain stationary although the air that forms them is moving rapidly, are known as "standing waves."

(A)  crests and troughs that remain stationary although the air that forms them is moving rapidly, are

(B)  crests and troughs that remain stationary although they are formed by rapidly moving air, are

(C)  crests and troughs that remain stationary although the air that forms them is moving rapidly, is

(D)  stationary crests and troughs although the air that forms them is moving rapidly, are

(E)   stationary crests and troughs although they are formed by rapidly moving air, is

The main challenge in this sentence is to observe the agree­ment of subject and verb (the resulting flow pattern... is known...) despite the distraction of a complex intervening structure containing several plural elements (with crests and troughs...). Choices A, B, and D can, therefore, be eliminated because they use an incorrect plural verb form, are. Choice E uses the correct verb form, is, but it incorrectly introduces a dependent adverbial although clause into a prepositional phrase (with crests ...). Choice D also makes this error. Such dependent clauses can only occur in the predicates of full clauses. C, the best choice, uses the correct verb form, is, and correctly puts the although clause inside the predicate of the relative clause (that... rapidly).

babydevil

E为什么不对？大家怎么上来就把E排除了？

ABCD都有个共同的严重问题，就是歧异,这犯了ETS的大忌。我们不知道到底是“人类制造石器工具”的时间被推前了还是“知道人类制造石器工具”的时间被推前了。这个歧异产生的根源是know作为从句谓语，使得date看起来好像指得是“know”发生的时间。

而E彻底解决了这个问题。是“已知制造石器工具的人存在的最早时间”被推前了。