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Scientists have dated sharp-edged flakes of stone found in

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

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New post 03 Sep 2007, 20:47
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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


I would think the answer should be E. ??
[Reveal] Spoiler: OA

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Last edited by carcass on 02 Feb 2017, 07:39, edited 1 time in total.
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Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

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New post 04 Sep 2007, 01:33
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alimad 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
[/u]

I would think the answer should be E. ??


C,

.........date at which something is known to .....is correct idiom
f.e: date at which the portrait is known to have been sold...

E is unidiomatic, completely.

we can say date of event {birth, death...test} f,e: we can say date of his {her, Ann`s} birth, but 'date of ' is not used directly with people or living things.

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

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alimad 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
[/u]

I would think the answer should be E. ??


A wrong tense.. Have dated so have made should be used instead of had made.. Also it seems to refer to scientists
B Had made suggested that it is not being done any more.Also it seems to refer to scientists
C correct --have dated and have made llel and earliest date at which - idiomatically correct
D to be making wrong tense and idiom
E humans who were known - changes meaning and also wrong tense

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

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New post 01 Dec 2009, 08:23
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alimad 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
[/u]

I would think the answer should be E. ??



:beat

Can anyone please explain all the option of this question?

:help2

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

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New post 01 Dec 2009, 08:53
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Dated at or Date at is correct idiom , so A,D, E are out

in B, "it" is ambiguous;
C looks better

hence C
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Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

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New post 01 Dec 2009, 09:08
srini123 wrote:
Dated at or Date at is correct idiom , so A,D, E are out

in B, "it" is ambiguous;
C looks better

hence C


Thanks Srini :)

Last edited by swatirpr on 02 Dec 2009, 20:27, edited 1 time in total.

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

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New post 31 Jul 2010, 20:44
I am with C as well. Whats the OA? Please share the OA

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

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New post 02 Aug 2010, 09:41
OA is C.

good question though. quite difficult to remember all the idioms.

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

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New post 02 Aug 2010, 10:26
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date at which is the correct idiom..
Hence C
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Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

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New post 28 Jan 2012, 11:13
Could someone please explaine "Have made" in C?

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

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New post 06 May 2012, 13:51
Runner2 wrote:
Could someone please explaine "Have made" in C?


I have the same question.
as per previous discussions, "have made" is || with "have dated". I think it is wrong because "have dated" referes to scientists and current time, but "have made" to people who lived thousand of years ago.

why is present perfect used?

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

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alimad 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.


[/u]

I would think the answer should be E. ??



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 : speaks about time not humans.
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Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

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New post 11 May 2012, 10:42
Code:
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 [u]when it is known that humans
made[/u] 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


OA:C
Background: Scientists have dated sediments. They found that the pieces of sharped-edged flakes were much older than samples previously found. This sentence structure has two parts that need to be parallel. The scientists have dated and the knowledge of the earliest date at which humans are to have made...

A: ...that humans made is not parallel to Scientists have dated INCORRECT
B: had made is also not parallel; so can be eliminated INCORRECT
C: at which humans are known to have made IS parallel to Scientists have dated CORRECT
D: to be making...not parallel INCORRECT
E: to make is not parallel because it is not in the PRESENT PERFECT tense INCORRECT

hope this helps guys....

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

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New post 11 May 2012, 10:56
Quote:
as per previous discussions, "have made" is || with "have dated". I think it is wrong because "have dated" referes to scientists and current time, but "have made" to people who lived thousand of years ago.


have made does not refer to to the people who lived thousands of years ago; however, it is modifying the earliest known date that is currently known (i.e the current theory, that these type of tools were only made 150,000 later)

Does this make sense?

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

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New post 01 Aug 2014, 00:47
'Dated at' is correct idiom , also sentence conveys correct meeting C wins :)
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Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

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

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

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New post 04 Sep 2017, 11:46
this is one of those problems from which you can learn about the ways in which these sorts of constructions are used. indeed, it is precisely from these sorts of problems that you must learn about the niceties of these constructions, as the gmat's usage can, and does, sometimes vary from that of other sources.

in this sort of construction, i'm pretty sure that either "when" or "at which" would be acceptable. (clearly, the latter is acceptable -- it appears in the correct answer, after all -- but i wouldn't object to the former.)
if you want to get really subtle, i think (not 100% sure) that "the date when" is used for actual, precise calendar dates, whereas "the date at which" is used for the usually more vague dates of historical events, such as the one in this problem. but i'm sure the test is not going to depend on this sort of nuanced difference.

i think the real problem with the construction in choice (a) is that the clause following "when" is "it is known". in other words, that choice suggests that the fact is (was?) known at that date, an interpretation that clearly doesn't make sense in context.
in the correct answer, the "at which" is followed by a clause whose subject is "humans", and which describes the actual action that took place at that date. therefore, i think the idea is that this clause more accurately describes the chronology of the events: i.e., the toolmaking happened at that date, and the fact is known now.

as for your other question, this isn't really a perfect tense, because it's actually not a tense at all -- it's an infinitive.
probably the easiest way to go here is to remember this as an idiomatic usage of the construction "known to". if the action is in the present, then you use "known to VERB"; if the action is in the past, then you use "known to have VERBed". as far as i know, these are the only two possible forms.
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Re: Scientists have dated sharp-edged flakes of stone found in   [#permalink] 04 Sep 2017, 11:46
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