Sentence Correction

scientist 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 make/ stone tools



when is is known that humans make
at which it is known that human had made
at which humans are known to have made
that humans are known to be making
of humans who were known to make.

I need someone to explain the options. Thanks,

I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.

logitech wrote:scientist 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 make/ stone tools



when is is known that humans make
at which it is known that human had made
at which humans are known to have made
that humans are known to be making
of humans who were known to make.

I need someone to explain the options. Thanks,

I Think it is B
as per [between 2.52 and 2.60 million years ago, pushing back by more than 150,000 ] humans made stones somewhere around say 2.52mn - 150000 so that period existed before 2.52 mn hence we need "had"

Correct me if i'm wrong.

i will go with C..

we need present perfect..

stone tools made in past are still there...

OA??

lol i would say that the answer is actually D....

here is why:

1. the reason for the highlighted area of the sentence is to to clarify to the reader what date the passage is referring to


2. to make the clarification author introduces characteristics of that date: i) presently we know that humans were making tools at that time ii) they were making tools at that time and continued as time propagated into the future


C says that the action has been completed => they were not making tools anymore => not true

B similar to C

E date is not one of the characteristics of the humans

A we are not referring to a point in time here but to a date which corresponds to that point in time

OA=?

IMO E.

A and B - IT reference is wrong.

C - Present tense. Do humans know how to make stone tools now?

D - THAT is not relevant here

E - correct answer. Uses simple past tense.

I will go for C

For sentences with comma the best way to find an answer is to put the part of the sentence following the comma at the start of the sentence

Pushing back by more than 150,000 years the earliest date at which humans are known to have made stone tools scientist 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 2.6 million years ago

the part in bold can be ignored as it is there only to confuse you

IMO C

when is is known that humans make<- Use of present tense is wrong
at which it is known that human had made <- Known to is right idiom..

at which humans are known to have made < -Correct use of Have made and Idiom Known to

that humans are known to be making <- Passive and use of making is wrong

of humans who were known to make. <- Dates cannot be OF HUMANS... Wrong[/b]

OA C

hitmewithgmat wrote:I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.

You rock dude! Thanks for the detailed explanation. I really appreciate it.

No problem Logitech!

hitmewithgmat wrote:I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.

could you explain the difference between known to and know that?
thanks

'Known that' is not correct usage.
'Known to' is correct idiom, which is a phrase whose meaning cannot be determined by the literal definition of the phrase itself, but refers instead to a figurative meaning that is known only through common use.

hemantsood wrote:'Known that' is not correct usage.
'Known to' is correct idiom, which is a phrase whose meaning cannot be determined by the literal definition of the phrase itself, but refers instead to a figurative meaning that is known only through common use.

I dont think Known that is an incorrect idiom:

Many - though certainly not all - of the investors who gave Madoff their money should have known that nobody has the financial chops to "opportunistically time" every purchase and get safely into treasuries every time the market drops. Even Warren Buffet ("the Oracle of Omaha") lost $25 billion last year.