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# Scientists have dated sharp-edged flakes of stone found in

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Intern
Joined: 20 Oct 2006
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Scientists have dated sharp-edged flakes of stone found in [#permalink]

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23 Oct 2006, 14:55
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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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VP
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23 Oct 2006, 17:09
Narrowed it down to A and C.

Since you are talking about a date here, you need when. So A it is.

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VP
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23 Oct 2006, 19:09
Tough one. Had to choose between A and C.

'date at which' and 'known to have made' sound idiomatic to me.

Would go with C.
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Director
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GMAT 1: 740 Q48 V42

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23 Oct 2006, 19:20
C

Can't think of explanations as to why the others are wrong. Sorry!

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VP
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23 Oct 2006, 19:38
Hmmmm

Between A and C....antecedent of it is doubtful

Looks like C but not sure ......

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24 Oct 2006, 02:31
kripalkavi wrote:
Since you are talking about a date here, you need when. So A it is.

Did you get this rule from the "stickys" ?

if "date at which" is ok, C sounds better
OA ?

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24 Oct 2006, 22:46
Insider wrote:
kripalkavi wrote:
Since you are talking about a date here, you need when. So A it is.

Did you get this rule from the "stickys" ?

if "date at which" is ok, C sounds better
OA ?

Got it from Princeton actually.
when to refer to date/time
where to refer to place

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26 Oct 2006, 06:52
when it is known that is awkward in A.

Clear (C) here.

date + at which~ in fine when estimating past actions

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Intern
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16 Nov 2006, 06:14
I've met this question at powerprep. The official answer is A

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16 Nov 2006, 20:36
Allen760 wrote:
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

And the OA is?

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Re: SC - Flakes   [#permalink] 16 Nov 2006, 20:36
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# Scientists have dated sharp-edged flakes of stone found in

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