Scientists have dated sharp-edged flakes of stone found in : GMAT Sentence Correction (SC)
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# Scientists have dated sharp-edged flakes of stone found in

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VP
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Scientists have dated sharp-edged flakes of stone found in [#permalink]

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18 Jan 2005, 09:08
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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.

A) when it is known that humans made

C) at which humans are known to have made

D)that humans are known to be making

E) of humans who were known to make
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Director
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18 Jan 2005, 09:28
I choose C too

A "it is know" is awkward, tense is not appropriate
B : exactly the same
C : sounds ok
D : that refers to date, improper tense
E : weird
Intern
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18 Jan 2005, 17:14
out of the five C sounds relativley good.
But can someone explain if "Date at which" is idiomatic ..it just didn't sound too good to me.
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19 Jan 2005, 06:42
I also like A. What is wrong with A? And is it proper to say "..date at which humans are known to have made"?

VP
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20 Jan 2005, 03:01
excuse me

Cound anybody know why A is wrong?

Thanks
SVP
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21 Jan 2005, 15:06
I'd choose C too. I think "at which" is preferable to "when". Humans are known to be doing something also sounds better than it is known that humans does something.
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21 Jan 2005, 19:29
C for me too. " when " in A sounds awkward. C seems right when put back in the original statement.
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27 Jan 2005, 21:16
Pick bt B and C for "at which". And (C) for "human's are known" vs "it is known".
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30 Jan 2005, 17:10
chunjuwu..
30 Jan 2005, 17:10
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