Scientists have recently found evidence that black holes—regions of sp

Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Subject-Verb Agreement + Parallelism + Comparison + Grammatical Construction

• Semicolons and the “comma + conjunction” construction are used to link two independent clauses; commas are used to link an independent clause with a dependent one; comma cannot be used to join two independent clauses.
• Any elements linked by a conjunction (“and” in this sentence) must be parallel.
• A comparison must always be made between similar things.

A: This answer choice fails to maintain parallelism between "that the black holes...exist at the core of nearly all galaxies" and "the mass of each black hole is proportional to its host galaxy"; please remember, any elements linked by a conjunction ("and" in this case) must be parallel. Further, Option A incorrectly compares "the mass of each black hole" to "its host galaxy"; please remember, a comparison must always be made between similar things.

B: Correct. This answer choice correctly refers to the plural noun "black holes" with the plural verb "exist". Further Option B maintains parallelism between "that the black holes...exist at the core of nearly all galaxies" and "that the mass of each black hole is proportional to its host galaxy". Additionally, Option B correctly compares "the mass of each black hole" with "that (mass) of its host galaxy". Besides, Option D correctly uses conjunction ("and" in this sentence) to join the dependent clauses "that the black holes...exist at the core of nearly all galaxies" and "that the mass of each black hole is proportional to its host galaxy".

C: This answer choice incorrectly compares "the mass of each black hole" to "its host galaxy"; please remember, a comparison must always be made between similar things. Further, Option C incorrectly uses the "comma + conjunction ("and" in this sentence)" construction to join the dependent clauses "that the black holes...exist at the core of nearly all galaxies" and "that the mass of each black hole is proportional to its host galaxy"; please remember, conjunction is used to join two parallel dependent clauses, and the "comma + conjunction" construction is used to join independent and dependent clauses.

D: This answer choice incorrectly refers to the plural noun "black holes" with the singular verb "exists". Further, Option D incorrectly uses the "comma + conjunction ("and" in this sentence)" construction to join the dependent clauses "that the black holes...exist at the core of nearly all galaxies" and "that the mass of each black hole is proportional to its host galaxy"; please remember, conjunction is used to join two parallel dependent clauses, and the "comma + conjunction" construction is used to join independent and dependent clauses.

E: This answer choice incorrectly refers to the plural noun "black hole" with the singular verb "exists". Further, Option E fails to maintain parallelism between "that the black holes...exist at the core of nearly all galaxies" and "the mass of each black hole is proportional to its host galaxy"; please remember, any elements linked by a conjunction ("and" in this case) must be parallel.

Hence, B is the best answer choice.

All the best!
Experts' Global Team

Basically I was confused between B and C I rejected B because of usage of That of can anyone explain how usage of that of is correct in B and why C is wrong

C is wrong because it compares "mass of black hole" to "the parent galaxy" (instead of comparing to the parent galaxy's mass). Invalid comparison.

B all the way!

I suggest a split pattern approach

the core structure should be: Scientists found evidence that [clause 1] and that [clause 2]
or
Scientists found evidence that [clause 1] and [clause 2]
(Both are acceptable)

[Clause 1]: black holes, .....[modifier], probably exist at the core of nearly all galaxies => plural Subject go with plural Verb => We eliminate D & E
[Clause 2]: the mass of each black hole is proportional to ........

There is a very clear patter
A - B - C with "Exist at the core of nearly all galaxies......."
D - E with "Exists at the core of ......"

From [Clause 1], as "black holes" is plural subject => need plural verb => eliminate D - E immediately as "exists" is in the singular form.

Now the case is
(A) exist at the core of nearly all galaxies and the mass of each black hole is proportional to
(B) .......................(like A)...................... and that the mass of each black hole is proportional to that of
(C) .......................(like A)....................., and that the mass of each black hole is proportional to

The 2rd pattern to split will be:
A - C: exist at the core of nearly all galaxies(,) and (that) the mass of each black hole is proportional to
B: ...................................................................................................is proportional to that of

At this step I will question the difference between A-C and B.
When we look closer to the [Clause 2], it is clear that "the mass of each black hole" should be proportional to the mass of something else, as A proportional to B only if A and B are equally sign.

In A - C, the mass of each black hole is proportional to its host galaxy => although I'm not an astrologer, and don't know what is the "mass", it don't make sense together

While in B, the mass of each black hole is proportional to that of (that of=the mass of) its host galaxy

==> at the end, eliminate A - C,

B is the only left one.

Remove the parenthetical stuff to get a clear idea of Subject-Verb agreement
Scientists have recently found evidence that black holes—regions of space in which matter is so concentrated and the pull of gravity so powerful that nothing, not even light, can emerge from them—probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.


The sentence now becomes
Scientists have recently found evidence that black holes probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.

"Black holes+exist & that" will be the correct construction with respect to parallelism and SV agreement

D and E are wrong outright

Among A,B,C
A is out Wrong parallelism becauses it is missing "that"
exist at the core of nearly all galaxies and the mass of each black hole is proportional to. needs a "THAT" after "and "for correct parallelism.

C is out
Wrong comparison .. compares mass of the black hole to the galaxy itself
exist at the core of nearly all galaxies, and that the mass of each black hole is proportional to

B is correct
compares mass of the black holes to that of the parent galaxy
(B) exist at the core of nearly all galaxies and that the mass of each black hole is proportional to that of

Two concepts are tested here.

1) SV agreement
2) Comparison

Subject " Black Holes " plural needs plural verb

D and E gone.

Comparison needs to be between mass of the BH and mass of host galaxy.

B uses both these concepts correctly.

Time taken : 30 sec

Hello GMATNinja,

While Option C is incorrect because it compares dissimilar entities, can we look at the ,and construction and state that it is incorrect?

In general, I don't think it's a good idea to overreact to commas on the GMAT, partly because style experts disagree about comma rules, and partly because the GMAT has better things to worry about. In (C), I don't see any need for the comma, since the two "that" phrases ("that black holes... probably exist" and "that the mass of each black hole is proportional...") are parallel to each other. In this case, it's basically a "list" of two subordinate clauses, so no need for a comma.

But you're very, very unlikely to see an official GMAT question in which the comma is the deciding factor.

I hope this helps!

Could anybody please tell me why there is "that" between "and" and "the mass of" in correct answer?

kimhoon27 The repetition of a structuring word such as "that" often helps us to see the intended meaning and structure. Scientists have found evidence of two things: THAT black holes exist and THAT the mass is proportional.

Scientists have recently found evidence that black holes—regions of space in which matter is so concentrated and the pull of gravity so powerful that nothing, not even light, can emerge from them—probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.

(A) exist at the core of nearly all galaxies and the mass of each black hole is proportional to --Incorrect comparison between mass and galaxy

(B) exist at the core of nearly all galaxies and that the mass of each black hole is proportional to that of --Correct

(C) exist at the core of nearly all galaxies, and that the mass of each black hole is proportional to --Same error as in A

(D) exists at the core of nearly all galaxies, and that the mass of each black hole is proportional to that of --SV disagreement

(E) exists at the core of nearly all galaxies and the mass of each black hole is proportional to that of --Same error as in A and D

Scientists have recently found evidence that black holes—regions of space in which matter is so concentrated and the pull of gravity so powerful that nothing, not even light, can emerge from them—probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.

(A) exist at the core of nearly all galaxies and the mass of each black hole is proportional to

(B) exist at the core of nearly all galaxies and that the mass of each black hole is proportional to that of

(C) exist at the core of nearly all galaxies, and that the mass of each black hole is proportional to

(D) exists at the core of nearly all galaxies, and that the mass of each black hole is proportional to that of

(E) exists at the core of nearly all galaxies and the mass of each black hole is proportional to that of

Split #1: The first verb in our choice refers to the plural noun "black holes". Hence, the verb has to be in plural form as well, which is "exist". Consequently, we can eliminate all answers that start with the singular form "exists" - answers D) and E).

Split #2: The comparison. We compare the mass of each blackhole with that of its host galaxy by saying that there is a proportional relationship between the two. To build a proper comparison we need to use "that of" at the end of the answer choice. By doing that we get "[...] that the mass of each black holo is proportional to that of its host galaxy". This is a correct comparison. As answers A) and C) lack this proper comparison, we can preclude them.

This leaves us with B) as the correct answer. It can also be noted that A) and E) don't maintain parallelism because they lack a "that".

Hope that helps

Hi,

I strongly disagree with this point. There is no problem in parallelism in option A. Although, second usage of "that" is preferable but I won't count out the option as wrong just on that basis of lack of "that".

Any comments?

Regards

Hi,

wouldn't a lack of "that" suggest that "Scientists have recently found evidence" and "the mass of each black hole is proportional" are the two main things that happened?
By the use of "that" it becomes clear that scientists found that X and that Y.

I understand your concern but I think that a lack of "that" changes the meaning. However, I'm not 100% sure.

daagh, could you shed some light on this question please?

Masterscorp


The basic concept of using that in two-part sentences.
If Something does two things, those things must be presented parallelly in structure and meaning joined by the introducing connector 'that.' For example. we may say that
<John reported to his wife that he got 800 in GMAT and that it all happened because of her help >
We need the connector that because of the two equally important things.
Rule No 2. If you are reporting only one thing and if the second part is n independent event not related to the first, then the golden rule is that there must be a comma before the word 'and' to forewarn that a new clause is about to begin
In my example, we might re-write the whole thing if we drop the 'that'.
John reported to his wife that he got 800 in GMAT,
and it all happened because of her help. But still one can see the disconnect in that legitimately grammatical clause
In other words, when we write compound sentences with two independent terms, then there must necessarily be a comma before the fanboys conjunction

I fully agree with Masterscorp

GMATNinja what function does dash sign have in this senntence ?

Scientists have recently found evidence that black holes—regions of space in which matter is so concentrated and the pull of gravity so powerful that nothing, not even light, can emerge from them—probably exist at the core of nearly all galaxies and the mass of each black hole is proportional to its host galaxy.

i chose actually D ....i thought "nothing" refers to 'exists"

you can answer this question on the weekend when you are in better mood

Hello dave13,


Although this question is not for me, I would be glad to help you out with this.


In this official sentence, the two dashes have been used as a comma pair to enclose some extra description, in this case the description of the black holes.


As far as your choosing Choice D as the correct answer is considered, I would say that Choice D and E are the easiest choices to reject because the SV number agreement error is the easiest to spot.



Hope this helps.
Thanks.
Shraddha