Navigators have known for thousands of years that the ocean has

What's wrong with D?

People say that "have" should be "has"
Is it impossible to see D in the way that a clear picture of ~ and what caused them HAVE emerged ?

Hi,

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.

Choice D: there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them.

Since we need to ascertain the subject for the verb "have emerged", let us ask, what emerged? The answer is "a reasonably clear picture". This is an entity in singular number. So, what is this picture about? This picture is about the patterns of ocean currents and what caused them. Pronoun "them" refers to "currents" and not the picture. Also "what caused them" is associated with the "ocean currents" and not the "picture". Hence, the use of plural verb "have emerged" for a singular entity "a reasonably clear picture" is not correct. We need a singular verb here. Choice A is the only answer with correct verb tense.

Hope this helps.
Thanks.
Shraddha

i pick A. B is wordy, in my point of view C, D and E are nonsensical and a bit awkward. correct me if i am wrong. by the way whats the source of this question?

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

First let us break the SC into clauses

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

In the above clauses the 4 th clause is the underlined portion.

Process of elimination.

Choice B . a reasonably clear picture of the patterns of ocean currents and their causes have emerged -in the 4 th clause the subject is "clear picture" so the verb should be singular but in the option "have emerged" is plural and "theirs" referring to "clear picture".So B is wrong

Choice C a reasonably clear picture emerged of ocean currents, their patterns and the causes of them - here in this we do not have any verb reffering to the subject of the clause "clear picture".So C is incorrect

Choice the subject of the clause "clear picture" is singular but the verb "have is plural" so D is wrong

Choice D "their" which is plural refers to subject of the clause "clear picture" which is singular so E is wrong


The final answer is "A"

I hope the explanation helps.Please correct if I am wrong.

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
Correct.

B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged
Wrong. main subject - a picture ==> singular ==> "have" is wrong.

C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
Wrong. "them" refers to ocean currents --OR-- patterns? ==> pronoun problem.

D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them
Wrong. There have... a clear picture ==> S-V agreement.

E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes
Wrong. "had emerged" (Past perfect) is not necessary. "their" refers to patterns --OR-- currents?

Hope it helps.

The core here is the cue phrase ‘in the last half century”, which is a range of time that extends up to the current day, rather than a specific point of time. Hence we have to use a present perfect tense to describe the verb: Second point is that the verb has to be singular to be in consonance with the singular subject picture. The pronouns , if at all required, should also be singulars. Which one has these two combinations? Only A, one may find.

Am I the only one who believes that "of the patterns" after the verb is a very awkward construction?

is it a picture of the patterns and causes of ocean currents that has emerged? or a picture has emerged of something?
this is ambiguous, and very strange!
I dismissed A just because of this. i have never seen before such a construction.

@e-gmat, if possible, please explain.

It implies the picture of the patterns and causes of ocean currents has emerged." Picture" out here implies the reason behind the patterns; it does not imply the literal meaning of picture. It’s like saying " I got the picture" or "The picture is clear to me".

I did GMAT Prep yesterday and this was one of the missed questions. I have no doubt on the correct or wrong answer anymore, but I do on the use of "has emerged" before "of the patterns...". As a foreign language native, I "hear" this "of the patterns..." modifying emerged instead of picture. Can anyone help me with this?

As per my understanding...

Picture of < X and Y >.... HAS

Here the Subject is Picture..so Singular Verb < HAS>
So B is incorrect!

Regards,
Abhishek SInha

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. - Correct
B. a reasonably clear picture of the patterns of ocean currents and their causes have emerged. - Subject verb agreement issue - picture has
the intended meaning of the sentence is that a clear picture of 2 things has emerged:
-- the patterns of ocean currents
-- the causes of ocean currents
"clear picture" is not paired with anything else.
C. a reasonably clear picture emerged of ocean currents, their patterns and the causes of them - parallelism issue
D. there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them. - "there have emerged ... a picture" - singular subject, plural verb
"the patterns of ocean currents and what caused them" (WORSE PARALLELISM)
... versus "the patterns and causes of ocean currents" in other choices (BETTER PARALLELISM)
E. there had emerged a reasonably clear picture of the patterns of ocean currents and their causes - usage of past perfect

Answer A

Ron from MGMAT-->
actually, "in the last half-century" REQUIRES the present perfect, because it's an indefinite period of time that extends up to the present.
similarly, you must use the present perfect with any of the following constructions:
"within the last (TIME PERIOD)..."
"since (DATE)..."
"for the last (TIME PERIOD)..."

This question is based on Subject-Verb Agreement and Construction.

Option B has a subject-verb disagreement – the plural verb ‘have’ does not agree with the singular subject ‘a reasonably clear picture’. So, Option B can be ruled out.

Option C has a tense error. The simple past tense ‘emerged’ is inappropriate as the time conveyed is of the recent past. The present perfect tense is more appropriate. So, Option C can be ruled out.

Options D and E have a different construction in which the subject is placed after the verb.
However, the subject in Option D is ‘a reasonable clear picture’. The plural verb ‘have’ does not agree with the subject. So, Option D can be ruled out.

In Option E, the past perfect tense ‘had emerged’ is inappropriate as the sentence conveys an action in the recent past. So, Option E can be ruled out.

Subject-Verb agreement is maintained in Option A; the singular verb ‘has’ agrees with the subject ‘a reasonably clear picture’. Therefore, A is the most appropriate option.

Jayanthi Kumar.

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 --> CORRECT use of present perfect tense in singular form

(B) a reasonably clear picture of the patterns of ocean currents and their causes have emerged --> Incorrect S-V agreement with singular "picture"

(C) a reasonably clear picture emerged of ocean currents, their patterns and the causes of them --> Awkward, wordy and non-parallel construction with the "and" conjunction

(D) there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them --> Incorrect S-V agreement with singular "picture"

(E) there had emerged a reasonably clear picture of the patterns of ocean currents and their causes --> There is no reason to to use past perfect "had emerged"

I've spent quite some time trying to understand this one.
Learn a great deal from this one.

1.) A long prepositional modifier phrase after a short predicate is acceptable!
2.) Again, be careful with the meaning.

My answer was B. Apparently, it is wrong.
My initial understanding was
a ...clear picture of patterns ... and their[ocean currents] causes have emerged.
I dont think the problem is with Subject and Verb agreement but instead with meaning!
After considering it for a while, I then realize it about the meaning...
in the last half-century that a picture and ocean causes have emerged! ---- Doesn't make any sense.
No way ocean causes have emerged in the last half-century.

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 [of] causes of ocean currents
(B) a reasonably clear picture of the patterns of ocean currents and their causes have emerged

I fully agree that B,C,D,E are all clearly wrong. However, can we say that A is wrong as well, because present perfect tense 'has emerged' is used with a specific time 'in the last half century'? From my understanding, the use of present perfect with specific time is wrong in all situations and should be replaced with past tense instead.

Any one mind giving their opinions on this? Thanks!

Hello smackmyface,

We hope this finds you well.

Having gone through the question and your query, we believe that we can help resolve your doubt.

The use of present perfect tense in a sentence that otherwise indicates that the relevant action concluded in the recent past or continues to affect the present (as the phrase "in the last half century" does here) is not incorrect; such usage is merely redundant. The same principle also applies to the use of the past perfect tense in sentences that otherwise indicate the order of events that concluded in the past, for example through the mention of times or dates or the use of terms such as "before/after/when/earlier/later". Relatedly, please keep in mind that redundancy is not a deal-breaker on the GMAT. An answer choice that features redundancy can very well be correct, so long as it is error-free and there are no other error-free answer choices more concise than it is. Redundancy should only be used to determine which is the best among otherwise error-free answer choices.

We hope this helps.
All the best!
Experts' Global Team

it says ''in the last half century'' is this a past time marker and should we use simple past? How to distinguish when we get 'last' mentioned in the sentence.