Nuclear fusion is the force that powers the Sun, the stars, and

Even when a VERBing functions as a modifier, it retains aspects of a verb.
SC29 in the OG12: The end of the eighteenth century saw the emergence of prize-stock breeding, with individual bulls fetching unprecedented prices.
Here, fetching serves as an adjective modifying bulls.
At the same time, fetching is given a DIRECT OBJECT (unprecedented prices).
This construction is viable because fetching is not only a modifier but also a VERB FORM, and a verb form may take a direct object.

OA: Nuclear fusion is the force that powers the Sun, the stars, and hydrogen bombs, merging the nuclei of atoms rather than splitting them apart, as nuclear reactors do.

One purpose of do is to stand in for the SIMPLE PRESENT TENSE form of an antecedent verb form.
In the OA above, do is standing in for the simple present tense form of splitting, which -- like fetching in SC29 -- is a verb form functioning as a modifier.
Since splitting retains aspects of a verb, it may serve as an antecedent for do.
Conveyed meaning:
Nuclear fusion is the force that powers the Sun, the stars, and hydrogen bombs, merging the nuclei of atoms rather than splitting them apart, as nuclear reactors split [them apart].
Here, split = the simple present tense form of splitting.
The words in brackets are omitted but implied.

Hello again, TheUltimateWinner. You are keeping me busy on this question. The merging phrase (sometimes called a verbal phrase) is indeed functioning as an adjective, but that does not mean that we can ignore the verb that has been tucked away within the phrase. For instance, if I write, Skating down the hill, I fell and hurt my knee, and so did my friend, only he was wearing pads, I cannot ignore the skating part and assume that my friend simply fell (i.e. without skating). The verb to do evidently has a broader application than you are giving it.

Were you confused about the original sentence? I see you have left it in your query.

- Andrew

At the very least, this kind of parallelism changes the meaning of the original sentence kadamhari825.

The original (and quite logical) intended meaning is that Nuclear fusion powers X, Y, and Z, BY merging the nuclei of atoms.

In other words, merging is the mechanism by way of which Nuclear fusion powers X, Y, and Z.

However, D is saying that Nuclear fusion does two independent (and mostly not-interrelated) things: Nuclear fusion -

i) Powers X, Y and Z
ii) Merges the nuclei of atoms

As an aside, D uses passive voice (as is done in nuclear reactors), thereby not making the doer of the action very evident.

Hi Guys,

Need help why D and E are incorrect.

EducationAisle has a nice breakdown of why (D) is incorrect in the post above.

And (E) is incorrect because it contains a faulty comparison: "nuclei of atoms, unlike atomic reactors." It doesn't make a whole lot of sense to compare nuclei to nuclear reactors.

The writer seems to be trying to convey the idea that nuclear fusion does one thing (merges nuclei) and nuclear reactors do a different thing (breaks nuclei apart.)

In other words, we want to contrast actions here. This is what (C) does, with its use of "as." (E) illogically compares nouns with "unlike."

I hope that helps!

Hey GMATNinja

Perfectly make sense. Thank you so much.

Hi GMATGuruNY AjiteshArun DmitryFarber - in (c) what does "as nuclear reactors do" modify ?

I thought "as nuclear reactors do" refers back to the verb in the main clause.

Main clause = [subject - (Nuclear fusion) and verb (to-be verb - is)]

Hence (C) is saying --

Nuclear fusion is the force that powers x,y and z, , as nuclear reactors (are the force that powers ....)

But, nuclear reactors are naturally not a force, making (C) illogical

Hence i chose (A) even though (A) has problems too.

Hello jabhatta2,

We hope this finds you well.

To answer your query, "as nuclear reactors do" modifies the verb phrase "splitting them apart".

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

Thanks ExpertsGlobal5 GMATGuruNY - why is "as nuclear reactors do" only modifying "splitting them apart" and not the OTHER verb "merging the nuclei of atoms"

What is the generic rule behind this ?

Hello jabhatta2,

We hope this finds you well.

To answer your query, "as nuclear reactors do" only modifies "splitting them apart" because "merging the nuclei of atoms" and "splitting them apart" are linked by the conjunction "rather than", which conveys that the two elements are in contrast with one another.

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

ExpertsGlobal5 - hmmm any reason why "as nuclear reactors do" IS NOT REFERRING back to the verb in main clause (verb in the main clause is the to-be verb : IS) ?

I thought adverbial phrases refer to the main verb in the clause.

I dont think adverbial phrases REFER to the CLOSEST verb (to the adverbial phrase)

LINKING VERBS include is, was, are, and were.
Each of these verbs serves to express not an action but a STATE-OF-BEING.
does/do/did may NOT stand in for a state-of-being.
These verbs may stand in only for ACTIONS.
Incorrect:
Mary is a fast runner, as does her brother.
Here, does cannot stand in for the antecedent verb is.
Correct:
Mary is a fast runner, as IS her brother.
Also correct:
Mary runs fast, as does her brother.
Here, does correctly stands in for runs (an antecedent action).

OA: Nuclear fusion is the force that powers the Sun, the stars, and hydrogen bombs, merging the nuclei of atoms rather than splitting them apart, as nuclear reactors do.
Here, do cannot stand in for is.
As a result, it is crystal clear that do is standing in for the simple present tense form of the preceding action splitting, as discussed in my earlier post.



This is certainly not a hard-and-fast rule.
An OA in GMATPrep:
Members are likely to be enrolled in lower-end insurance plans that require doctors to see more patients, spending less time with each.
Here, COMMA + spending modifies NOT the main verb (are) but the nearest preceding action (to see) and the agent of this action (doctors).
Conveyed meaning:
When DOCTORS SEE more patients, they will as a result be SPENDING less time with each patient.

Hi jabhatta2, our book EducationAisle Sentence Correction Nirvana discusses this aspect of "to do" verbs. Have attached the corresponding section of the book, for your reference.

Hello jabhatta2,

We hope this finds you well.

To answer your query, as GMATGuruNY has explained, it is not a rule that the adverbial modifier will always refer to the main verb in a clause or modify the entire clause as a whole.

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

D says:

Nuclear fusion is the force that powers the Sun, the stars, and hydrogen bombs, and merges the nuclei of atoms but does not split them apart, as is done in nuclear reactors.

in this sentence the that is the essential modifier, and the and is the connector. for the connector and the powers and the merges are parallel to each other. In this version, the sentence actually says that...
....the force powers and the force merges

This is not the actual meaning here... the meaning is because of Nuclear fusion's powers something happen (merges)... In short, merging is the direct result of Nuclear fusion is the force that powers the Sun, the stars, and hydrogen bombs

Hi GMATNinja
Please help here..Have been racking my brains but can't figure out. Now i really hate this question:

How do we know that what nuclear reactors do?
I mean, how do we know what "as nuclear reactors do" refers to?
Is it just ''merging the nuclei of atoms instead of splitting them apart'' or just to ''splitting them apart''

Thanks!

You could make the same argument about choices (A), (B), and (D), and since (C) has a better comparison structure than those three, we can cross them out. For more on why those three can be eliminated, check out these two posts:

• https://gmatclub.com/forum/nuclear-fusion-is-the-force-that-powers-the-sun-the-stars-and-30022.html#p2499393
  
• https://gmatclub.com/forum/nuclear-fusion-is-the-force-that-powers-the-sun-the-stars-and-30022-20.html#p2935787

As explained in this post, the "unlike" seems to illogically compare "atomic reactors" to the noun right before it (nuclei of atoms). It's okay to use "unlike" to compare two nouns (e.g. "nuclear fusion" and "atomic reactors"). But if that's the comparison we want, it would be much clearer to put the "unlike" part at the beginning of the sentence.

Also, the parallel structure in (E) makes it sound as though nuclear fusion does two distinct things: (1) it powers the sun/stars/bombs, and (2) it merges the nuclei of atoms. That's not quite right -- the merging is HOW the fusion powers those things, not a separate and unrelated action.

As for (C), you make a very fair point, but the fact that we have "rather than" in between "merging" and "splitting" makes it fairly clear that the reactors do the latter -- it would be tough to argue that we should leapfrog "splitting" and pair reactors with the "merging" instead.

If we wanted to suggest that the reactors also merge the nuclei of atoms, it would be much better to write something like this:

"... merging the nuclei of atoms, as nuclear reactors do, rather than splitting them apart."

Luckily, this is a fairly old question, so if you aren't convinced, don't lose any sleep over it!