The energy source on Voyager 2 is not a nuclear reactor, in which atom

Question

The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken  apart; rather  a kind of nuclear battery that uses natural radioactive decay to produce power.

(A) apart; rather 
(B) apart, but rather 
(C) apart, but rather that of 
(D) apart, but that of 
(E) apart: it is that of

Verbal Question of The Day: Day 120: Sentence Correction 
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https://www.nytimes.com/1989/08/26/us/voyager-s-heartbeat-is-nuclear-battery.html

This energy source is not that of a nuclear reactor, in which atoms are actively broken apart,  but rather  a kind of nuclear battery that uses natural radioactive decay to produce power.

GMATNinja · Accepted Answer

This one is short and sweet. Nice way to end the week, no?

Hopefully, the semicolon jumps off the page at you immediately. In general, semicolons need to separate full, independent clauses. (There's also a rare usage in which semicolons can separate items in a list of individual items that already contain commas, but that's unlikely to cause you much pain -- an official example is available  here .) In this case, the semicolon makes no sense: "rather a kind of nuclear battery..." is not a full, independent clause. (A) is out.

This looks fine. "The energy source is not a nuclear reactor..., but rather a kind of nuclear battery." It's a classic "not X, but rather Y" sort of construction, and it makes logical sense: we're clarifying that the energy source is something other than what we might expect. And there are no semicolon issues. Let's keep (B).

If you've ready our post on  the GMAT's many uses of the word "that" , then the "that of" construction should leap off the page at you. "That" is used as a singular pronoun here, so your job is to figure out what the singular pronoun refers back to... and then reread the sentence to make sure that it actually makes sense.

OK, so what are our options for singular referents for "that"? Well, there's "the energy source" or "a nuclear reactor." Let's try both of those, and see if either of them work:

"The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart, but rather  the energy source  of a kind of nuclear battery that uses natural radioactive decay to produce power." --> Huh? That's just weird and redundant, and doesn't really make sense. We could say that the energy source IS a nuclear battery, but "the energy source is...  the energy source  of a kind of nuclear battery" really doesn't work.  
 "The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart, but rather  a nuclear reactor  of a kind of nuclear battery that uses natural radioactive decay to produce power." --> Nope, that's even worse.

So (C) is out.

(D) has exactly the same error as (C). Removing the word "rather" doesn't change the fact that the pronoun is completely nonsense.

(E) has the same mistake as (C) and (D). And we can probably argue about the "it", too. But either way, (E) is gone, and (B) is the best of the bunch.

egmat · Answer

Hi,

The prerequisite for any clause is that it must have a subject and it must have a verb. Presence of SV pair makes a clause, either a dependent or an independent.

This sentence can be divided into following clauses:
 
The energy source on Voyager 2   is  not a nuclear reactor (Independent Clause) (blue = subject, green = verb)

in which  atoms   are  actively  broken  apart (Dependent clause)

rather a kind of nuclear battery

that   uses  natural radioactive decay to produce power. (dependent clause)

"rather a kind of nuclear battery" is not a clause because it does not have any verb. Together, this phrase and the last clause build a dependent clause that appears after the semicolon. This is the incorrect sentence structure.

Also note that for every clause, IC or DC, the SV pairs must be independent. The verb of one clause cannot play the role of verb for the subject of another clause.

The sentence that you have cited is correct. "it" in the beginning of the second IC correctly refers to "The energy source on voyager 2" because they both are placed in the subject position of the ICs. This is from the grammatical standpoint. Logically also "it" refers to the same because the second IC is talking about "nuclear battery" which is a kind of "energy source" only.

Hope this helps.
Shraddha

https://e-gmat.com/blogs/wp-content/uploads/2012/01/shraddha.jpg

r019h · Answer

think of it like this-

B) the energy source is not X, but rather a kind of Y

C) the energy source is not X, but rather that of a kind of Y

C is unnecessary and changes the meaning of the sentence, hence answer is B

u0422811 · Answer

Answer is B.

You can not use a semicolon since you do not have two independent clauses.

The following can not stand alone on its own:

Rather a kind of nuclear battery that uses natural radioactive decay to produce power.

It is dependent on the preceding clause. It is also unidiomatic. The idiom is - "not X, but rather Y"

So you have to stick with it. This eliminates A and E.

Parallelism eliminates C and D.

not a nuclear reactor, but rather a kind of battery. Adding that messes it all up.

Hope this helps.

whamberto · Answer

I have chosen B for this question:

A. This answer choice does 2 things incorrectly - it splits the comparison into 2 independence clauses and the second clause is a fragment. There is no reason to include a semicolon because it is splitting up the comparison into 2 sentences.

B. This answer is correct because it follows the not X, but rather Y comparison. Also, the elements are parallel.

C. This answer is incorrect. Although it does follow not X, but rather Y, "that of" is a relative pronoun that refers to nothing.

D. "That" does not refer to anything.

E. Again, the semicolon is unnecessary because we want a sentence that clearly describes the comparison in one thought.

alwaysudit · Answer

the question uses a "not x ...but rather y" type of construction. I am confused that in such a case is "but" acting as a coordinating conjunction i.e. it must be followed by a complete clause . If so please tell me which is the main verb in the clause followed by but i.e." a kind of nuclear battery that uses natural radioactive decay to produce power"?

EducationAisle · Answer

Actually it is not just  but , but  not X but Y .

X is a phrase: a nuclear reactor (,in which atoms are actively broken apart)
Y is also a phrase: rather a kind of nuclear battery (that uses natural radioactive decay to produce power)

I have put the modifiers (relative clauses) in brackets above to make it clear that the actual phrases are  a nuclear reactor  and  a kind of nuclear battery .

In fact, I can't think of any scenario where  Not X but Y  would have  complete clauses  in X and Y. Does something come to your mind? Would be interesting to see.

alwaysudit · Answer

Thankyou so much Ashish ,that was very useful. So , I can safely conclude that every usage of "but" doesn't necessitate it to be used as a conjunction.

EducationAisle · Answer

There is one more thing. It looks from your earlier post that you did realize that this question uses  not x ...but rather y  type of construction. B, C and D are the three options that use this construct and  none  of these options uses a clause after  but .

Hence the entire debate about whether a  clause  must be used after  but  is a moot point for this question; I understand though that your question was perhaps for a larger understanding and not necessarily limited to this question alone.

However, in general, test-takers should in fact develop an  eye  for seeing what  really matters  for a question.

The reason I want to highlight this is that students get worked-up on issues that don't matter for a question. This happens very often with questions where students think that a pronoun has ambiguous reference. We suggest students that if the same pronoun  ambiguity  exists in all 5 options, then  move on , because in that case, clearly pronoun  ambiguity  is not being tested there; the same way as  clause  after  but  is not getting tested here: ).

Countdown · Answer

I read it somewhere that 'but' and 'rather' convey the same contrast so need of clubbing them together, is it ?

I saw a question in OG verbal where the two were clubbed together.The question is there in the attachment :?:

Attachment:

sentence _correction.jpg [ 36.2 KiB | Viewed 74357 times ]

.

sentence _correction.jpg .

VeritasPrepRon · Answer

Hi Countdown, I'm not sure where you read that differentiation, but it seems a little oversimplified.

Rather usually implies some kind of comparison, usually that I want this rather than that, as in preference.

But is a much more general term, it generally means some kind of dissidence, but it's definition is broader. (see what I did there?)

This answer is really governed by the "not" on the first line. Voyager 2 is  not x, but rather y . This is an idiom that can be expected on the GMAT.

You could also turn the phrase to say something like: It is not x, rather it is y. That's fine too. But rather on it's own (answer choice A) does not make it sufficiently clear that we're still talking about Voyager 2.

Hope this helps!
-Ron

egmat · Answer

Hi Aris, Thanks for posting your doubt here. :-)

Choice E is incorrect because there is no grammatical or logical antecedent for the pronoun phrase that of . Please note that that the subject pronoun it in the second independent clause in this choice already stands for The energy source on Voyager 2 . It is enough to say: The energy source on Voyager 2 is not a nuclear reactor; it is a kind of nuclear battery. There is absolutely no need for the pronoun phrase that of in Choice E. This is the reason why this choice is incorrect. Hope this helps.

Thanks. Shraddha

TeamGMATIFY · Answer

The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken  apart; rather  a kind of nuclear battery that uses natural radioactive decay to produce power.

Meaning and analysis:
The energy source on Voyager 2 is not a nuclear reactor but rather (is ) a kind of nuclear battery
"in which atoms are actively broken apart" -> is a modifier modifying nuclear reactor
that uses natural radioactive decay to produce power -> is a modifier modifying nuclear battery

(A) apart; rather -> rather is a conjunction and cannot be used with a Semi colon. Semi colon joins two Clauses.

(B) apart, but rather -> Correct

(C) apart, but rather  that  of
Comparing nuclear reactor with "that" of battery. Not sure what is referred by "That"

(D) apart, but  that  of
Comparing nuclear reactor with "that" of battery. Not sure what is referred by "That"

(E) apart :  it is  that  of 
1) Normally, colon is used to provide examples or long fragments in the list. I think, semi colon would have been appropriate
2) Comparing nuclear reactor with "that" of battery. Not sure what is referred by "That"

anox · Answer

The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken  apart; rather  a kind of nuclear battery that uses natural radioactive decay to produce power.

Issues:  Idiom | Comparison

Analysis:
 1. In this sentence, two sources of energy are compared.
2. The construction of sentence should be "... not X but rather Y", where X and Y should be comparable entities such as "a nuclear reactor" and "a kind of nuclear battery"
 
 (A)  apart ;  rather 
 - Clause connected via semi-colon should be independent, whereas in this case, second clause is not independent

(B)  apart,  but rather

(C)  apart, but rather  that of  
 - "That of" creates meaning issue

(D)  apart,  but that of  
 - "That of" creates meaning issue

(E)  apart :  it is that of
 - No contract is created by this option. A conjunction to create contrast is necessary here to coney proper meaning.

Answer:   (B)

daagh · Answer

The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken  apart; rather  a kind of nuclear battery that uses natural radioactive decay to produce power.

(A) apart; rather 
(B) apart, but rather 
(C) apart, but rather that of 
(D) apart, but that of 
(E) apart: it is that of

The simple solution to this is: 
1. The energy source is either a reactor or a battery. not that of a battery. We can ruthlessly dismiss C, D, and E. 
Between A and B; A is wrong because A is a fragment as it is displaying a phrase rather than IC after the semicolon. B is the winner. 
 I don't think there is any need to unnecessarily indulge in other splits, or meanings etc

daagh · Answer

One basic factor in this topic is that the energy source is equated with a nuclear reactor in the non-underlined part. It is not talking about the source as 'that of' a nuclear reactor. Therefore, any mention of the phrase 'that of ' in the second part is an unparallel comparison since we are comparing an energy source with something of another energy source namely the nuclear battery. 
We can simply dump C, D, and E on this count. Of course, in A the second part after the semicolon is not an IC.
B is the indisputable winner.

Novice90 · Answer

Hi,

Can someone please explain why do we need to use "but rather" and not only "rather" here?

As pointed above, is it not redundant?

egmat · Answer

Hello Novice90 , I will be glad to help you out with this one.

Since the phrase but rather appears in the correct answer choice of this official question, the expression is most certainly NOT redundant. The sentence uses the contrast word but to bring out the intended contrast. ABC is not X but Y. Now, the word rather does NOT present contrast, and hence, its usage with but does NOT lead to redundancy. The word rather is used either to present preference or to mean somewhat. It is the second meaning that the usage of the word rather denotes in the correct answer choice. So basically, this sentence intends to say that the energy source on Voyager 2 is not a nuclear reactor but somewhat a kind of nuclear battery. Hope this helps.

Thanks. Shraddha

ratsvijay · Answer

can someone help me with this, semicolon and comma+fanboy are both used to join 2 IC's. If A is wrong, so should be B as it is using comma+but.

The energy source on Voyager 2 is not a nuclear reactor, in which atom

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GMAT Sentence Correction (SC - EA only) Questions

The energy source on Voyager 2 is not a nuclear reactor, in which atom

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