T-4-Q1 天山-7-41

chamcham

T-4-Q1
                天山-7-41

Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools.

1. when it is known that humans made

2. at which it is known that humans had made

3. at which humans are known to have made

4. that humans are known to be making

5. of humans who were known to make

The key is C, A seems not clear when refer to which time ( the time we KNEW the fact that human made stone tool VS. the time human made stone) and only the latter has logical meaning. Is "it" also wrong since it has no reference? I feel like it is just anticipatory subject, correct? 

 

Another question is: are both the following usages correct?

 

1. date when + clause

2. date at/on which + clause

thanks for help,

carolinelmf

你的理解是对的，A会造成歧义。而it是指代后面的that从句，纯语法上说。

关于date，请查字典。

chamcham

thx for the reply. About the generalization, any help?

Are both the following usages correct?

 

1. date + when + clause

2. date + at/on which + clause

s7s7

嗬嗬

s7s7

我的观点，at which更清晰

chamcham

I saw a lot of example on nytime for at which, but did see some date when as well. So are both valid?

flyuo2006

我对为什么没有疑问,但是at which修饰的是known还是made啊? C好象有修饰歧义.. 

annajulira

请问B错在哪里呢?

makedream

B）。。。the earliest date at which it is known that humans had made stone tools.

“the earliest date” 应该是指人类用石器的时间，但是 “it is known” （知道“人类用石器”的时间）插在之前，变成修饰  “the earliest date” ，改变原来意思。

A 有同样问题。

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http://bbs.taisha.org/thread-1230795-1-2.html

http://www.urch.com/forums/gmat-sentence-correction/90013-sets-sc7.html#post586667

gundam00