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Intern
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Scientists have dated sharp-edged flakes of stone found in [#permalink]
 23 Oct 2006, 15:55
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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
B. at which it is known that humans had 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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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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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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the way is difficult, but perfect trust makes it easy.
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Director
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C
Can't think of explanations as to why the others are wrong.  Sorry!
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VP
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Hmmmm
Between A and C....antecedent of it is doubtful
Looks like C but not sure ......
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Intern
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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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VP
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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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Current Student
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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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I've met this question at powerprep. The official answer is A
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VP
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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
B. at which it is known that humans had 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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