The discovery that Earths inner core rotates independently of and more

The discovery that Earth’s inner core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth’s magnetic field.

A. core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of the flow of heat from the inner through the
outer planet and of the formation and periodic reversal in direction of Earth’s magnetic field - Correct

B. core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of how heat from the inner core flows through
the outer planet, and the formation and periodic reversal in direction of Earth’s magnetic field

How X and the formation -> are not parallel
,and -> Comma and suggests there are more than three items in the list.

C. core rotates independently and more quickly than Earth’s outer layers are responsible for advancing studies of how heat from the inner core flows through
the outer planet, and how Earth’s magnetic field forms and the periodic reversal of its direction
The discovery - are

D. core, rotating independently and more quickly than Earth’s outer layers, are responsible for advancing studies of the flow of heat from the inner through the
outer planet, and the formation and periodic reversal in direction of Earth’s magnetic field
The discovery - are

E. core, rotating independently of and more quickly than Earth’s outer layers, is responsible for advancing studies of the flow of heat from the inner through the
outer planet and of how Earth’s magnetic field forms and the periodic reversal of its direction

This option changes the meaning. The original sentence states that Discovery that Earth's Inner Core independently of and more quickly than Y is responsible.
In this option, The discovery of Earth's inner core is responsible.
"rotating independently of and more quickly than Earth’s outer layers" is a modifier for Inner Core.

Points to be noted are -

1) S/V agreement - The discovery that..... IS ( eliminate C and D)
2) || ism - is responsible for advancing studies OF X ... and OF Y ( Eliminate B and E)

A is the rt answer

I agree in toto; This is the crux of Sentence Correction in GMAT: to be able to eliminate first a good number of choices, through identifying the more visible mistakes and then to go into nuances in the rest to narrow down to the best answer

@daagh,Brian, Q1) regarding the prepositional parallelism, do we really need an "of" after "and"? Both of you have emphasized on this, so I would like to get this concept straight.

Wouldn't both of below sentences hold correct?
"Discovery is responsible for studies of heat flow and magnetic field".
"Discovery is responsible for studies of heat flow and of magnetic field".

Q2) This highlighted structure in A "the flow of heat from the inner through the outer planet" made me leave this choice. Shouldn't there be a qualified noun for the adjective "the inner" in the specified phrase?

A. core rotates independently of and more quickly than Earth’s outer layers is
responsible for advancing studies of the flow of heat from the inner through the
outer planet and of the formation and periodic reversal in direction of Earth’s
magnetic field -correct prallele and correct use of verb form
B. core rotates independently of and more quickly than Earth’s outer layers is
responsible for advancing studies of how heat from the inner core flows through
the outer planet, and (missing parallelism 'OF') the formation and periodic reversal in direction of Earth’s
magnetic field - incorrect
C. core rotates independently and more quickly than Earth’s outer layers are
responsible for advancing studies of how heat from the inner core flows through
the outer planet, and how Earth’s magnetic field forms and the periodic reversal
of its direction - are here represents the discovery which is singlular. -incorrect
D. core, rotating independently and more quickly than Earth’s outer layers, are
responsible for advancing studies of the flow of heat from the inner through the
outer planet, and the formation and periodic reversal in direction of Earth’s
magnetic field - are here represents the discovery which is singlular. -incorrect
E. core, rotating independently of and more quickly than Earth’s outer layers, is
responsible for advancing studies of the flow of heat from the inner through the
outer planet and of how Earth’s magnetic field forms and the periodic reversal of
its direction -- awkward sounding = out


IMO A

Hi EducationAisle,

As discussed long back (yes I am preparing again), wrt "10.9. Modifier-clauses ending in preposition are incorrect" of your book, we have "independently of" in the above construction? What am I missing?

Thanks

Hi Rohit, good morning! Section 10.9 of Sentence Correction Nirvana specifically mentions that clauses (especially relative clauses) ending in a preposition, are not preferred on GMAT.

Here, the sentence is:

The discovery that Earth’s inner core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth’s magnetic field.

So, basically the core of the clause that we are discussing is:

Earth’s inner core rotates independently of and more quickly than Earth’s outer layers

In other words,

Earth’s inner core rotates independently of Earth’s outer layers.

Hopefully it is easy for you to see that this clause is not ending in a preposition.

Following are few examples from Official sources, where section 10.9 will in fact apply, since all the following have clauses that end in a preposition. Notice that in all these cases below, typically it is the relative clause that is ending in a preposition (hence our recommendation in the book you need to specifically look out for relative clauses ending in a preposition).

In each of the following cases, I have highlighted the incorrect modifier in red, and have also marked the preposition in bold.

GMATPrep (option B):
Because the numbers 1 and 2 and the letters A and B have connotations they are aware of, companies conducting consumer taste tests of foods or beverages typically choose numbers such as 697 or 483 to label the products.

OG 13, #83 (option D):
A report by the American Academy for the Advancement of Science has concluded that many of the dioxins that are currently uncontrolled and North Americans are exposed to come from the incineration of wastes.

OG Verbal Review, #20 (Option D):
Declining values for farm equipment and land, which farmers use as collateral to borrow against to get through the harvest season, are going to force many lenders to tighten or deny credit this spring.

p.s. I just happened to see this post of yours. Going forward, if you are looking for my specific inputs, request you to PM me.

'The discovery' is singular. C and D are out.

A. core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth’s magnetic field discovery is responsible for studies OF the flow of heat and OF the formation and reversal. Correct parallelism

B. core rotates independently of and more quickly than Earth’s outer layers is responsible for advancing studies of how heat from the inner core flows through the outer planet, and the formation and periodic reversal in direction of Earth’s magnetic field. discovery is responsible for advancing studies OF how heat , and the formation and periodic reversal. OF is missing in the second part of sentence.

E. core, rotating independently of and more quickly than Earth’s outer layers, is responsible for advancing studies of the flow of heat from the inner through the outer planet and of how Earth’s magnetic field forms and the periodic reversal of its direction . 'The discovery that earth's inner core is responsible for advancing studies' is not the intended meaning, 'The discovery that earth's inner core rotates is responsible' is the intended meaning

I also did not choose option A, as it is unclear what "inner" refers to, does it imply inner planet or inner layers or inner core? Experts please advise!

Posted from my mobile device

Hi GmatBawse, B has an issue with parallelism. Clearly, from a parallelism perspective, the structure of B is:

....responsible for advancing studies of X and Y, where:

i) X: how heat from the inner core flows through the outer planet, (this is a clause)

ii) Y: the formation and periodic reversal in direction of Earth’s magnetic field (this is a phrase)

Since X and Y are the logically similar parts of the sentence, these parts must be grammatically similar as well. However, while X is a clause, Y is a phrase. Hence, X and Y are not grammatically similar. So, option B fails the parallelism test.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses Parallelism in Phrases and Clauses, its application and examples in significant detail. Have attached the corresponding section of the book, for your reference.

Hi JarvisR,

Thank you for your question. While some of the other commenters are on the right track, here is how I tackled the question myself. I began by noting the most obvious differences between each possible answer, then reducing down answers based on those differences. Let's start with what I noticed right away:

1. Punctuation = some of the answers used a comma + and, but others didn't

2. Parallel structure = especially with the two ways studies were advanced (at the end of each answer)

Let's start with #1 on our list. We know that by using the comma + and, it creates two independent clauses that are separated by a comma and a conjunction. So this means whatever comes after the comma MUST be able to stand alone as a complete sentence. Let's look at each answer that uses the comma + and to see if ONLY what comes after the "and" can stand alone:

B. the formation and periodic reversal in direction of Earth’s magnetic field (NO = fragment)
C. how Earth’s magnetic field forms and the periodic reversal of its direction (NO = fragment)
D. the formation and periodic reversal in direction of Earth’s magnetic field (NO = fragment)

Since none of these are able to stand alone, they can't come after a comma + and. We can rule out these answers, which leaves us with A & E.

If we look at #2 on the list, we can figure out if both answers use parallel format. Let's only block out the parts we want to focus on: the two ways the studies were advanced:

A: of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth’s magnetic field (uses parallel structure = CORRECT)

E: of the flow of heat from the inner through the outer planet and of how Earth’s magnetic field forms and the periodic reversal of its direction (does NOT use parallel structure = WRONG)

Since answer E doesn't use parallel structure, we're left with answer A, which is the correct answer.

I still can't get

The discovery that Earth’s inner core rotates independently of and more quickly than Earth’s outer layers..

after "independently of" a phrase comes without "earth's outer layers"... what kind of construction is this? I would be convinced if it were like "... independently of earth's outer layers and more quickly than earth's outer layers ..."

what's exactly wrong with E in terms of parallelism? I cannot still see, could you please indicate?

faltan , this kind of construction is an elliptical construction.

• One object [Earth's outer layers] can be attached to two different prepositions [OF and THAN, respectively], and the object need not be repeated.

• This structure is correct, in which we have CORE ROTATES + preposition + preposition + DIRECT OBJECT OF BOTH PREPOSTIONS

-- The discovery that Earth’s inner core rotates independently of and more quickly than Earth’s outer layers . . .

-- That construction is elliptical. One mention of the same direct object is removed, because
the object Earth's outer layers distributes "backwards" to the prepositional word "of" and to the prepositional word "than."

-- Alternatively, we can recognize that the preposition OF legally "hops over" the second prepositional phrase in order to connect with Earth's outer layers.

-- The construction may "sound" stilted or forced. Very few people speak this way, but in written English
two prepositions that take the same object can be stated one after the other.
The object gets mentioned only after the second preposition.

SPOILER ALERT: ANSWER TO AN OFFICIAL QUESTION
From OG 2018, SC #754, which can be found HERE

Correct answer: The first trenches cut into a 500-acre site at Tell Hamoukar, Syria, have yielded strong evidence that centrally administered complex societies in northern regions of the middle East arose
Similar correct examples:
She was fiercer than and not afraid of her creepy neighbor.
World Leader #1 spoke glowingly about and acted like a desperate puppy around World Leader #2.

Takeaway: If two prepositional phrases have the same direct object, then often there is no need to repeat the direct object.

Hope that analysis helps.

faltan , please narrow your question.
I cannot figure out what part of the analysis you are missing.

EMPOWERgmatVerbal pays attention to the second part of E, which is both not parallel and utterly nonsensical.
That astute analysis addresses neither the subject of sentence E nor its verb.
The analysis does not need to cope with either the subject or the verb.
That said, perhaps an overall sense of the sentence would expose the parallelism issues in option E.

Two suggestions:

1) Try to answer this question: what IS parallel in option E? Why? (Or, what, exactly, is RIGHT with E in terms of parallelism?)

2) Try to find the structure of the sentence. Write the option into the sentence.

• Remove the non-essential modifier in E and its commas.
-- That is, remove all of this: , rotating independently of and more quickly than Earth’s outer layers,
-- Write or type the sentence out.

• Compare to A
-- The subject in (A) is "the discovery that Earth’s inner core rotates [a certain way]."
The subject in A is not "the discovery that."
The verb phrase in (A) = IS responsible for. Then what? Is responsible for . . . ??? [Find the parallelism.]

• Now look at (E).
Subject? Is there a verb? What follows that subject and verb/no verb? [Look for the parallelism. Does it exist?]

If you can frame a more specific question, perhaps using one or both of the suggestions, it will be easier for us to answer you.

to be more precise, indeed "of the flow of heat from the inner through the outer planet and of how Earth’s magnetic field forms and the" does not seem to have any problem with parallelism. Flow is noun and how the ... is phrase?.. that's why?

faltan , not quite. "How" is a noun in this case.

The problem? It's subtle: There are three nouns.

In A, two of the three are combined.

In E, the three are separate. The third noun is not parallel.

A) The discovery that Earth’s inner core rotates independently of and more quickly than Earth’s outer layers is responsible

for

advancing studies

of the (1) flow of heat from the inner through the outer planet

and

of (2) the formation [of] and (3) periodic reversal in direction of Earth’s magnetic field.

We have to address meaning, which is not mechanical.

The second prepositional phrase in A is compound.

It refers to
(2) the formation of Earth's magnetic field AND
(3) the periodic reversal of Earth's magnetic field

Think of a whirlpool.

First comes the formation of the whirlpool.
Then, after the whirlpool is formed, it starts reversing direction at regular intervals.

Or it is formed, and a nanosecond LATER it reverses direction. Formation and reversal of direction are not the same.

In A, the two events are combined by elliptical construction into ONE prepositional phrase . . .
in which "formation [OF]" and "direction of" both take the direct object Earth's magnetic field.

In A the prepositional phrase structure is 1 and (2 and 3).

In E, the last two events are not connected. Now there are three events listed separately.

In E, the prepositional structure is 1 and 2 and 3.
1 and 2 are parallel. 3 is not.

E) The discovery that Earth’s inner core, rotating independently of and more quickly than Earth’s outer layers,
is responsible

FOR

advancing studies

1) OF the flow of heat

and

2) OF how Earth’s magnetic field forms

and

3) the periodic reversal of its direction.

There is no OF attached to the third item.

"How" can be a noun that means the manner in which.

But the periodic reversal of its direction is not parallel. It lacks the word OF.

Hope that helps.