Navigators have known for thousands of years that

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NandishSS: Master | Next Rank: 500 Posts; Posts: 366; Joined: Fri Jun 05, 2015 3:35 amFollowed by: 2 members; Thanked: 3 times

by NandishSS » Sun May 21, 2017 9:36 pm

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Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.

A.a reasonably clear picture has emerged of the patterns and causes of ocean currents.
B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged.
C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them.
E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes.

OA:A

Source:GMATPrep EP2

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Source: Beat The GMAT — Sentence Correction | Sun May 21, 2017 9:36 pm

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Mon May 22, 2017 2:16 am

NandishSS wrote:Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.

A. a reasonably clear picture has emerged of the patterns and causes of ocean currents.
B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged.
C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them.
E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes.

In B and D, picture (singular) does not agree with have emerged (plural).
Eliminate B and D.

C: Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture emerged of ocean currents.
Here, the meaning conveyed by the red portion (a picture of ocean currents emerged ONLY IN THE LAST HALF CENTURY) contradicts the meaning conveyed by the blue portion (navigators have known FOR THOUSANDS OF YEARS that the ocean has variable currents).
Eliminate C.

In E, it is not crystal clear whether their serves to refer to patterns or to currents.
Since A avoids this ambiguity and is free of errors, eliminate E.
Also, there is no justification for the usage of the past perfect (had emerged).

The correct answer is A.

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meenakshimiyer: Senior | Next Rank: 100 Posts; Posts: 39; Joined: Sat Jan 12, 2019 1:08 am

by meenakshimiyer » Sat Jan 12, 2019 8:51 pm

Here, "a clear picture" is the subject which is Singular. So, we need to use Singular verb "has" instead of plural verb "have". Use of "have" violates S-V agreement. Hence, Choice B and D are out. Answer choice C and E are out because of the use of wrong tense. The sentence is in present perfect tense while Choice E uses past perfect and Choice C uses simple past tense. Hence, A is the answer.

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vietnam47: Master | Next Rank: 500 Posts; Posts: 110; Joined: Thu Apr 26, 2018 11:19 pmFollowed by: 1 member

by vietnam47 » Sat Aug 10, 2019 9:12 am

NandishSS wrote:Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.

A.a reasonably clear picture has emerged of the patterns and causes of ocean currents.
B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged.
C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them.
E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes.

OA:A

Source:GMATPrep EP2

for some time indicators such as "in" and "for", both simple past and present perfect are fit, depending on logic. "in' and 'for" can show a period in the past, and, so, past forms are used, or a period which continue until present, and, so, present perfect is used. this is basic knowledge explained in grammar books. time indicators and contexts are focus of discussion of tenses.
I learned gmat this morning. now is afternoon. this morning is past. past simple is used
I have learned gmat this morning. now is in this morning. this morning is a period from a point of past to now.
I have learn gmat for many years, but only yesterday, I passed it.
this is correct.
so, i think that "emergED" , a past verb, is good in C. C is wrong because of " cause of them". this phrase is wordy and change the meaning

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gui_guimaraes: Senior | Next Rank: 100 Posts; Posts: 38; Joined: Thu Dec 17, 2015 9:22 am

Re:

by gui_guimaraes » Mon Jul 27, 2020 8:59 am

GMATGuruNY wrote: ↑
Mon May 22, 2017 2:16 am

NandishSS wrote:Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.

A. a reasonably clear picture has emerged of the patterns and causes of ocean currents.
B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged.
C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them.
E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes.
In B and D, picture (singular) does not agree with have emerged (plural).
Eliminate B and D.

C: Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture emerged of ocean currents.
Here, the meaning conveyed by the red portion (a picture of ocean currents emerged ONLY IN THE LAST HALF CENTURY) contradicts the meaning conveyed by the blue portion (navigators have known FOR THOUSANDS OF YEARS that the ocean has variable currents).
Eliminate C.

In E, it is not crystal clear whether their serves to refer to patterns or to currents.
Since A avoids this ambiguity and is free of errors, eliminate E.
Also, there is no justification for the usage of the past perfect (had emerged).

The correct answer is A.

Hi Mitch! @GMATGuruNY
Is C a run on sentence? "...a reasonably clear picture emerged of ocean currents, their patterns and the causes of them." tks!

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