Positing an enormous volcanic explosion at the end of the Permian

Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Parallelism + Verb Forms

• All elements in a list must be parallel.
• In modifying a noun, the past participle implies that the noun took an action that concluded in the past.

A: The sentence formed by this answer choice fails to maintain parallelism among "explain the presence of a buried crater", "account for the presence of the element iridium (originating deep within the earth)", and "the presence of quartz"; remember, all elements in a list must be parallel. Further, Option A incorrectly uses the present participle ("verb+ing" - "having" in this sentence) phrase "having been shattered" to refer to an action that concluded in the past; remember, the simple past tense is used to refer to events that concluded in the past.

B: Correct. The sentence formed by this answer choice correctly maintains parallelism among "of a buried crater", "of the element iridium (originating deep within the earth)", and "of quartz". Further, Option B correctly uses the past participle ("shattered" in this case) to refer to an action that concluded in the past; remember, in modifying a noun, the past participle implies that the noun took an action that concluded in the past.

C: The sentence formed by this answer choice fails to maintain parallelism among "explain the presence of a buried crater", "the element iridium (originating deep within the earth)", and "explain the presence of quartz"; remember, all elements in a list must be parallel. Further, Option C incorrectly uses the present participle ("verb+ing" - "having" in this sentence) phrase "having been shattered" to refer to an action that concluded in the past; remember, the simple past tense is used to refer to events that concluded in the past.

D: The sentence formed by this answer choice fails to maintain parallelism among "explain the presence of a buried crater", "the presence of the element iridium (originating deep within the earth)", and "explain the presence of quartz"; remember, all elements in a list must be parallel.

E: The sentence formed by this answer choice fails to maintain parallelism among "explain the presence of a buried crater", "explain the element iridium (originating deep within the earth)", and "the presence of quartz"; remember, all elements in a list must be parallel.

Hence, B is the best answer choice.

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



All the best!
Experts' Global Team

Topic Tested: Parallelism

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been shattered by high-impact shock waves. -- The original sentence is not parallel

A. account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been - Incorrect. Parallelism error.

B. of the element iridium (originating deep within the earth), and of quartz - Correct. would explain the presence of a buried crater, of the element iridium, and of quartz.

C. the element iridium (originating deep within the earth), and explain the presence of quartz having been - Incorrect. would explain the presence of x, y and explain the presence of z is not parallel again.

D. the presence of the element iridium (originating deep within the earth), and explain the presence of quartz - Incorrect. Parallelism error again.

E. explain the element iridium (originating deep within the earth), and the presence of quartz - Incorrect. Parallelism error.

Answer: B

But is follows presence of X and Of Y.

Posted from my mobile device

Could someone clarify how D is wrong?

Here is the sentence with D:
Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, the presence of the element iridium (originating deep within the earth), and [would] explain the presence of quartz shattered by high-impact shock waves.

Just before this post, I read:
https://gmatclub.com/forum/your-verbal- ... 46533.html
which suggests not be over fixated with true parallel structure to the hilt.
Shouldn't there be more than just parallelism error for us to eliminate choices?

Hi sevenplusplus, let's look at the sentence with D again:

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, the presence of the element iridium (originating deep within the earth), and explain the presence of quartz shattered by high-impact shock waves.

By the intended meaning of the sentence, hopefully it's clear would explain is trying to explain three elements. In D, the repetition of the presence in the second element suggests that the way to do (what we call as) XYZ deconstruct is:

Positing an enormous volcanic explosion at the end of the Permian period would explain

i) X: the presence of a buried crater
ii) Y: the presence of the element iridium (originating deep within the earth)
iii) Z: explain the presence of quartz shattered by high-impact shock waves.

Once we have done this deconstruct, the common portion of the sentence (in this case Positing an enormous volcanic explosion at the end of the Permian period would explain) should individually make sense with X, with Y, and with Z.

In D, this common portion is not making sense with Z, because the sentence would read:

Positing an enormous volcanic explosion at the end of the Permian period would explain explain the presence of quartz shattered by high-impact shock waves.

explain explain is clearly incorrect.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses this very powerful method of tackling parallelism (XYZ deconstruct) , its application and examples in significant detail. If someone is interested, PM me your email-id; I can mail the corresponding section.

Thanks for the reply. How do we know that "would explain" is "out" of the XYZ deconstruct? My argument is that it could be considered part of each X, Y, Z.


Sent from my iPhone using GMAT Club Forum mobile app

Sure. So, let's try putting would explain within the XYZ deconstruct.

Positing an enormous volcanic explosion at the end of the Permian period

i) X: would explain the presence of a buried crater
ii) Y: would explain the presence of the element iridium (originating deep within the earth)
iii) Z: would explain explain the presence of quartz shattered by high-impact shock waves.

Again, as is evident, Z (would explain explain the presence...) is incorrect.

Hi Vyshak ,

I have a doubt here. When do we use a comma before 'and'?
Usually its like a,b and c.
In what conditions, do we use- a,b, and c? and what's the difference?

Really appreciate if you or anyone on this forum can explain.

Regards,
ashygoyal

Hello Everyone!

This looks like a great example of a GMAT question that focuses on parallel structure! Let's go through each option carefully to narrow them down to the right answer! To get started, here is the original question:

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been shattered by high-impact shock waves.

(A) account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been
(B) of the element iridium (originating deep within the earth), and of quartz
(C) the element iridium (originating deep within the earth), and explain the presence of quartz having been
(D) the presence of the element iridium (originating deep within the earth), and explain the presence of quartz
(E) explain the element iridium (originating deep within the earth), and the presence of quartz

One important sign that we're dealing with parallelism is when the options are part of a list. Any time you see a list, it's a good idea to start by asking yourself, "Is each item in the list worded/structured similarly?" Let's take a closer look at each option to throw out any answers that aren't parallel. To make it easier to spot, I've included the non-underlined part of the list because everything MUST match that in structure, verb tense, and tone:

(A) would explain the presence of a buried crater,
account for the presence of the element iridium (originating deep within the earth),
and the presence of quartz having been

This option is NOT PARALLEL because each item in the list is introduced using a different verb, or none at all: explain / account for / no verb. Therefore, this is INCORRECT because it's not parallel.

(B) would explain the presence of a buried crater,
of the element iridium (originating deep within the earth),
and of quartz

This option is PARALLEL because each item is introduced in a similar manner (using the word "of"). It's much simpler and more concise, too! Therefore, this is the CORRECT option because it uses parallel structure.

(C) would explain the presence of a buried crater,
the element iridium (originating deep within the earth),
and explain the presence of quartz having been

This option is NOT PARALLEL because only 2 out of 3 items starts with "explain the presence of." For this to be parallel, all 3 items need to match. Therefore, this is another INCORRECT option!

(D) would explain the presence of a buried crater,
the presence of the element iridium (originating deep within the earth),
and explain the presence of quartz

This option is also NOT PARALLEL because it only uses the verb "explain" in 2 of 3 items in the list. They're very close to parallel, but not quite good enough! Therefore, this option is INCORRECT because it doesn't use parallel structure.

(E) would explain the presence of a buried crater,
explain the element iridium (originating deep within the earth),
and the presence of quartz

This option is NOT PARALLEL because each item uses different combinations of the phrases "explain the presence of," "explain," and "the presence of." For this to be parallel, all 3 items need to match. Therefore, this option is INCORRECT because it doesn't use parallel structure.

There you go - option B is the correct answer because it's the only one that uses parallel structure!


Don't study for the GMAT. Train for it.

Hi experts, my doubt is regarding the 'comma+and' construction here. Shouldn't it be an IC ? what am I missing here?

Typically, a "comma + and" construction will be used in one of two ways: 1) to separate two independent clauses or 2) to designate the end of a list of elements.

(B) is an example of the second situation. Here's the relevant portion of (B) again: "Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, of the element iridium (originating deep within the earth), and of quartz." The volcanic explosion can explain the presence of three elements: a buried crater, the element, iridium, and quartz. Because we have a list, it's appropriate to use "comma + and" to signal to the reader that the list is complete.

Also, the "rules" governing comma usage can be subtle and subjective, so you don't want to be too rigid when debating whether a comma is appropriate. You won't run across many GMAT questions that explicitly test whether the presence or absence of a comma is correct, so it's best to find more concrete reasons to eliminate answer choices. For more on punctuation on the GMAT, check out this video.

I hope that helps!

GMATNinja, the original sentence has the word crater in italics, and I don't quite understand why. Does it make sense to you?

I definitely don't see "crater" in italics on the original post on this thread, or in my copy of the 2020 OG. Are you looking at something other than the original post or the OG, maybe?

EducationAisle
Hi,
I've a curiosity to know one thing from you about choice D.

What if we remove the middle item from the choice D? Is it something like below?
Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater and (would explain) explain the presence of quartz shattered by high-impact shock waves.

Thanks__

Yeah looks fine from a parallelism perspective, though the duplication of explain in the second part, is redundant.

Hello experts AjiteshArun sayantanc2k EducationAisle VeritasKarishma

I chose option A on the basis of following reasoning.

I reasoned account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been as noun+noun modifier ( absolute phrase ) modifying a buried crater and underlined part is made parallel by connector ,and . i understood that option B is correct answer but where i am making mistake in understanding option A?

Thanks and regards.

Hi kadamhari825,

You may have gone for an unlikely meaning, which in turn would have led you to an unlikely structure (X would explain Y, account for A and B). The problem with this interpretation is that the buried crater can't be directly related to the iridium and the shattered quartz. Instead, the intended meaning of this sentence is that there are three things that positing an enormous volcanic explosion would explain: the buried crater, the presence of iridium from deep within the Earth, and the shattered quartz.

This is the sentence that option A leads to:

1. {X} would (a) explain the presence of a buried crater, (b) account for the presence of the element iridium (originating deep within the earth), and (c) the presence of quartz having been shattered by high-impact shock waves.

Explain is a verb form (it combines with would), and account is a verb form as well (again, it combines with would). Presence, however, is a noun, so the elements of the list aren't as parallel as in option B. Option A would have been better if it had three verb forms.