It is currently 25 Jun 2017, 10:34

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

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

Author Message
TAGS:

### Hide Tags

Intern
Joined: 27 May 2010
Posts: 11
Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

28 Aug 2010, 14:39
1
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

61% (01:00) correct 39% (01:13) wrong based on 293 sessions

### HideShow timer Statistics

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
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
[Reveal] Spoiler: OA
Senior Manager
Joined: 28 Jun 2009
Posts: 444
Location: United States (MA)
Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

28 Aug 2010, 23:16
C is correct.

Given : 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
stone tools.

I simplified the sentence to:

Scientists have dated tool2 to between x and y yrs ago, pushing back z yrs the date when it is known that humans made tools.

A. when it is known that humans made - un-referenced pronoun "it" - wrong
B. at which it is known that humans had made - wrong
C. at which humans are known to have made - Correct
D. that humans are known to be making - wrong
E. of humans who were known to make - wrong
Retired Moderator
Status: I wish!
Joined: 21 May 2010
Posts: 784
Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

29 Aug 2010, 16:56
Please underline the question. It's really difficult to understand the question without underline!.

Thank you.
_________________

http://drambedkarbooks.com/

VP
Joined: 17 Feb 2010
Posts: 1491
Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

29 Aug 2010, 17:06
Senior Manager
Joined: 28 Jun 2009
Posts: 444
Location: United States (MA)
Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

29 Aug 2010, 17:19
kissthegmat wrote:
Please underline the question. It's really difficult to understand the question without underline!.

Thank you.

The answer option A is always the underlined part from the given sentence. I don't think its necessary to underline it.
Manager
Joined: 09 Jun 2015
Posts: 101
Re: Scientists have dated sharp-edged flakes of stone found in [#permalink]

### Show Tags

15 Mar 2016, 05:45
1
This post was
BOOKMARKED
iDisappear 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

Here 'when' is used as an adverb after an expression of time to mean 'at which'.
'Sunday is the only day when I can relax.
The action 'relax' takes place on Sunday.
In the problem the action 'is known' takes place at a particular point of time in the past. It is incorrect. The correct action is 'humans made stone tools'.
Therefore, I think it is correct to say 'when humans made stone tools', or 'when human are known to have made stone tools'.
Both the structures are absent in the options.
But we can replace 'when' with 'at which'.
So, we have the correct option C
Re: Scientists have dated sharp-edged flakes of stone found in   [#permalink] 15 Mar 2016, 05:45
Similar topics Replies Last post
Similar
Topics:
36 Scientists have recently found evidence 12 19 Aug 2016, 10:04
8 Scientists have dated sharp-edged flakes of stone 3 12 Dec 2015, 14:13
9 Social scientists in the United States have found that 11 13 Oct 2015, 00:37
37 Scientists have dated sharp-edged flakes of stone found in 17 26 Oct 2015, 10:12
8 Scientists have dated sharp-edged flakes of stone found in 16 19 Sep 2016, 16:06
Display posts from previous: Sort by