El Niño, the periodic abnormal warming of the sea surface off Peru, a

Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Tenses + Grammatical Construction + Pronouns + Verb Forms

• The simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.
• The simple present continuous tense is used to refer to actions that are currently ongoing and continuous in nature.
• The present perfect tense (marked by the use of "has/have") is used to refer to actions that concluded in the past but continue to affect the present.
• "where" can only be used to refer to physical locations.
• For referring to the intent/purpose of an action, the infinitive verb form ("to + base form of verb" - "to + allow" in this sentence) is preferred over the present participle ("verb+ing" - "allowing" in this sentence).

A: This answer choice fails to form a complete sentence; as "combine" and "has accumulated" are both parts of a modifying phrase, there is no active verb to act upon the subject noun "El Niño". Further, Option A uses the present participle ("verb+ing" - "allowing" in this sentence) to refer to the purpose of the action "combine"; remember, for referring to the intent/purpose of an action, the infinitive verb form ("to + base form of verb") is preferred over the present participle.

B: This answer choice fails to form a complete sentence; as "are combining" and "is accumulating" are both parts of a modifying phrase, there is no active verb to act upon the subject noun "El Niño". Further, Option B incorrectly refers to the noun "phenomenon" with the pronoun "where"; remember, "where" can only be used to refer to physical locations. Additionally, Option B incorrectly uses the simple present continuous tense verb "are combining" to refer to a statement of universal fact; remember, statements of universal fact are best conveyed through the simple present tense, and the simple present continuous tense is used to refer to actions that are currently ongoing and continuous in nature. Besides, Option B incorrectly uses the simple present continuous tense verb "is accumulating" to refer to an action that concluded in the past but continues to affect the present; please remember, the present perfect tense (marked by the use of "has/have") is used to refer to actions that concluded in the past but continue to affect the present, and the simple present continuous tense is used to refer to actions that are currently ongoing and continuous in nature.

C: This answer choice fails to form a complete sentence; as "combine" and "is accumulated" are both parts of a modifying phrase, there is no active verb to act upon the subject noun "El Niño". Further, Option C incorrectly uses the simple present tense verb "is accumulated" to refer to an action that concluded in the past but continues to affect the present; please remember, the present perfect tense (marked by the use of "has/have") is used to refer to actions that concluded in the past but continue to affect the present, and the simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.

D: Correct. This answer choice acts upon the independent subject noun "El Niño" with the active verb "is" to form a complete thought, producing a complete sentence. Further, Option D avoids the pronoun error seen in Options B and E, as it uses the phrase "in which" rather than "where". Additionally, Option D correctly uses the simple present tense verb "combine" to refer to a statement of universal fact. Moreover, Option D correctly uses the present perfect tense verb "has accumulated" to refer to an action that concluded in the past but continues to affect the present. Besides, Option D uses the infinitive verb form ("to + base form of verb" - "to + allow" in this sentence) to refer to the purpose of the action "combine".

E: This answer choice incorrectly refers to the noun "phenomenon" with the pronoun "where"; remember, "where" can only be used to refer to physical locations. Further, Option E uses the simple present continuous tense verb "are combining" to refer to a statement of universal fact; remember, statements of universal fact are best conveyed through the simple present tense, and the simple present continuous tense is used to refer to actions that are currently ongoing and continuous in nature. Additionally, Option E incorrectly uses the present participle ("verb+ing" - "accumulating" in this sentence) to refer to an action that concluded in the past but continues to affect the present; please remember, the present perfect tense (marked by the use of "has/have") is used to refer to actions that concluded in the past but continue to affect the present.

Hence, D is the best answer choice.

To understand the concept of "Simple Tenses" on GMAT, you may want to watch the following video (~2 minutes):



To understand the concept of "Present Perfect Tense" on GMAT, you may want to watch the following video (~1 minute):



To understand the concept of "Simple Continuous Tenses" on GMAT, you may want to watch the following video (~1 minute):



To understand the concept of "Infinitives" versus "Present Participle" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team

would go with D

I may not explain it very well but here is what I think:
a,b c do not have a verb to complete the clause that began with El Nino, however d & e have IS that is completing the clause. The 'IN WHICH' in d is better than 'where' in E. also E sounds odd otherwise.

Why is has used in the correct choice D?

Can someone explain the Error in Option C... I know its wrong but can't figure out what it is. Thanks in advance!

Any one about usage of HAS in D?

has accumulated is a present perfect tense, and is primarily used to depict an event that has happened at some unspecific time before the current time.

Perhaps this can be best understood by few examples:

Now a days, the new Governments always rollback the changes that have been implemented by the old Governments.
- The clause in present perfect (that have been implemented by the old Governments) is modifying changes

Everyday, the Sun clears the mist that has been accumulated by the low temperatures of the night.
- The clause in present perfect (that has been accumulated by the low temperatures of the night) is modifying mist

In El Nino, changes combine to allow the warm water that has accumulated in the western Pacific to flow back to the east.
- The clause in present perfect (that has accumulated in the western Pacific) is modifying warm water

p.s. Our book SC Nirvana discusses Present Perfect tense, its application and examples in significant detail. If you can PM you email, I can send you the corresponding section.

Can someone explain why "combine" or "to allow" in A and B is not considered a verb?

combine in A and are in B are indeed verbs; but these verbs are only part of dependent clauses; so, there is no independent clause in A and B; and there cannot be a sentence without an Independent clause.

Let's take a simplified example that mirrors A:

James, a married man, an athlete who combines skill and strength enabling him to win medals.

This is not a valid sentence, because the verb combines only appears as a part of dependent clause: who combines skill and strength enabling him to win medals.

One way to fix it would be:

James, a married man, is an athlete who combines skill and strength to enable him to win medals.

Now, we have an Independent clause: James is an athlete

By the way, A and B also have back to back modifiers (the periodic abnormal ... and and a phenomenon in which....), modifying the same entity El Nino. This is not GMAT's stylistic preference.

El Nino, the periodic abnormal warming of the sea surface off Peru, a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated in the western Pacific to flow back to the east.

(A) a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated -- El Nino does not have a verb ; usage of allowing is incorrect
(B) a phenomenon where changes in the ocean and atmosphere are combining to allow the warm water that is accumulating -- El Nino does not have a verb ; usage of where to refer to a phenomenon is incorrect
(C) a phenomenon in which ocean and atmosphere changes combine and which allows the warm water that is accumulated -- El Nino does not have a verb ; meaning change because of usage of and
(D) is a phenomenon in which changes in the ocean and atmosphere combine to allow the warm water that has accumulated -- Correct
(E) is a phenomenon where ocean and atmosphere changes are combining and allow the warm water accumulating -- usage of where to refer to a phenomenon is incorrect ; present continuous are combining is incorrect

AjiteshArun , daagh , mikemcgarry ,GMATNinja ,egmat, other experts-- please enlighten
In the correct answer , is the usage of "to allow" correct? To allow should express intent/purpose

Answer D

To can be used for intent, but it has a whole lot of other uses too. In this case they're trying to get at result. For example,

The opening was large enough to allow only a small child through.

Here the meaning is not (a) for the purpose of allowing only a small child through the opening was large enough but (b) the size of the opening was such that only a particular result was possible.

Hi Puilunchristin,

Thank you for your question. Let's look at this question, one problem at a time, and see if we can narrow it down to the correct answer!

The first major difference between the answers is how they begin: a phenomenon vs. is a phenomenon. The problem with just using "a phenomenon" is that it creates a sentence fragment. There is no verb in the sentence - it's just a subject with two modifiers. So, let's get rid of answers A, B, & C because all three answers aren't complete sentences.

Now that we've narrowed it down to only D & E, let's look at what's different about each one:


(D) is a phenomenon in which changes in the ocean and atmosphere combine to allow the warm water that has accumulated

Answer D is the CORRECT answer because it uses the phrase "in which" to indicate an explanation, not the phrase "where" which indicates place or direction. It also uses clearer verbs "combine" and "has accumulated" to show meaning.

(E) is a phenomenon where ocean and atmosphere changes are combining and allow the warm water accumulating

Answer E is INCORRECT because it uses the word "where," which should only be used to show place or direction - NOT to indicate you are giving an example or explanation. The other problem is using verbs like "are combining" and "accumulating." They both tell the reader that this phenomenon is happening only RIGHT NOW, instead of saying it's something that happens in the past and could also happen in the present or future.

This is an interesting question.
If we do not read the underlined portion carefully along with the rest of the sentence, we might think that it is a modifier that should begin with ‘a phenomenon’.
But here, there is already a modifier after El Nino.

As a result, the options without the word ‘is’ end up as sentence fragments without a verb.

We can eliminate Options A, B and C for this reason.

Between Options D and E, Option D uses ‘where’ to refer to ‘phenomenon’. The correct usage is ‘in which’.

Eliminate Option E.

Option D is the best choice.

Hope this helps!

Hi,
It would have been correct if it had 'oceanic' and 'atmospheric'.
Hope this clears it.

Not really Yatharth; C does not have any main verb. Basically, there is no Independent clause in C (every complete sentence must have at least one Independent clause).

So, C is (what's called) a sentence fragment.

You can watch our video on Independent and Dependent Clauses.

A,B and C here are fragments
E incorrectly uses when and -ing form
D here is the correct answer

"Has" is used for present perfect tense which implies that the task has been carried out over the period of time and the task is still going on or its effect is still present in the present moment.

"Has" is used because logically water has accumulated over time and it's effect is still present i.e. the accumulated warm water is still present in the western Pacific.

Hi AjiteshArun

Below are the two versions of Option A after adding the main verb ''IS''. The only difference is a comma before ''allowing''
Are the below two sentences convey the correct and same meaning?

1. El Niño, the periodic abnormal warming of the sea surface off Peru, is a phenomenon in which changes in the ocean and atmosphere combine
allowing the warm water that has accumulated in the western Pacific to flow back to the east.

Here in ''changes in the ocean and atmosphere combine allowing'', does ''allowing'' modify the combine correctly? Its an adverbial modifier, right?

2. El Niño, the periodic abnormal warming of the sea surface off Peru, is a phenomenon in which changes in the ocean and atmosphere combine,allowing the warm water that has accumulated in the western Pacific to flow back to the east.

Thanks