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

I might be missing here something but aren't the answers:
A
E
out, not only because of subtle meaning issues but also because we are dealing here with run-on sentences. As mentioned by previous users, what comes after "and" in both cases are independent clauses, so connecting them (disregarding the meaning issues) we require a comma followed by a coordinate conjunction. Thus, we can get rid of A and D.
I am not 100% sure if we can assume the reverse to be also true (I would greatly appreciate some opinions on that), that once we use a comma followed by a coordinate conjunction what follows must be an independent clause (it seems to be implied by the answer offered by GMAT). But if that would be the case, we could also get rid of:
C
D
leaving B as the only viable option without tedious interpretation of the subtle meaning.

We may have addressed your questions here and here. Those posts also have a couple follow-up questions and answers, so you might want to check those out too.

If nothing in the thread helps, let us know!

Jack386
Short answer: no and no.

A comma is not required when we use a conjunction to join two independent clauses. It's very common, and some sentences might fare poorly without it, but we don't absolutely have to have it. For instance, I might say "I'm cold and I want to go home." There's just not enough complexity to warrant a comma.

On the flip side, we definitely don't have to have an independent clause after every instance of comma + and. The simplest example is a list, where we might end a sentence with something like ", and monkeys." However, we might see a comma in almost any places where it clarifies the meaning or structure, and we commonly see commas used to set off modifiers. So if I have two nouns or phrases joined with AND, and then I want to add a modifier in between them, I will end up with "comma + and" without an independent clause after.

He voted for Bill X, angering his supporters, and Bill Y, alarming his enemies.

We can also use comma + and to set off a modifier at the end of a sentence:

She wears a heavy jacket every day, and not just in the winter.

I actually only eliminated A because of the comparison, but I was wondering about the reasoning of the first part of your analysis in A. In your example about the Knicks, could we not say that "I believe that Santa Claus is real and the Knicks will win the 2018 NBA title." works because the first 'that' "distributes" out to the Knicks to mean the following: "[I believe that] Santa claus is real and [I believe that] the Knicks will win the 2018 NBA title"?

I also question the statement regarding the Knicks ("And it seems that the latter clause is a fact, rather than something I BELIEVE is true.") because it's not an independent clause. I would be inclined to agree if the structure included a comma before the and, then it's without a doubt a separate unrelated fact.

I know you don't like to nitpick about comma usage, but I feel as though this might still be parallel in it's current form.

I'm not 100% sure, so I would greatly appreciate your input. Thanks!

GMATNinja

Interesting question!

Maybe there's a better way to frame the choice about whether to use "that" for the clause about the Knicks. I would argue that the first option is totally unambiguous, because it's clearly stating that I have two beliefs: one about Santa and one about the Knicks. Whereas in the second example, there's more than one way you might interpret it: perhaps the "that" applies to both clauses, or perhaps we have two independent thoughts.

Moreover, without the second "that," you might read the first part of the second sentence "I believe that Santa Claus is real and," and anticipate that you're about to get another description of Santa: "I believe that Santa Claus is real and very lazy," or "I believe that Santa Claus is real and needs to learn to respect boundaries," for example.

So when you see "I believe that Santa Clause is real and the Knicks..." you might initially feel as though you're reading nonsense. Of course, you can figure out what's actually going on by rereading, but the use of "that" prevents this confusion in the first place.

In other words, I want something to clarify the sentence. If I use a comma, you're right, it sounds as though I have two independent ideas, so that's not a great solution. Ultimately, I think you've got a point that the second sentence isn't definitively wrong or illogical, but it's not as good as the clearer alternative in which we use "that."

In essence, it's less about right and wrong, and more about degrees of clarity.

I hope that helps!

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
The mass of each balck hole is proportional to its host galaxy- Incorrect comparison. Eliminate.

The mass of each black hole is proportional to the mass of its host galaxy or
The mass of each black hole is proportional to that of its host galaxy

(B) exist at the core of nearly all galaxies and that the mass of each black hole is proportional to that of
The use of “that of” corrects the comparison error present in Option A.
Scientists have found evidence
- That blockholes exist at the..
- And that the mass of each black hole is proportional to that of its host galaxy. Correct

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

(D) exists at the core of nearly all galaxies, and that the mass of each black hole is proportional to that of
The singular verb “exists” doesn’t agree with the plural subject “black holes”. Eliminate

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

Vishnupriya
GMAT Verbal SME

I hope I am doing the elimination correctly

Scientists have recently found evidence (that black holes probably exist at the core of nearly all galaxies) and (that the mass of each black hole is proportional to that of.)

A- Mass of black hole ---should be compared with mass of galaxy not galaxy itself
B- Mass of black hole --- compared with that (mass) of galaxy ( comparing apples with apples)
C - Mass of black hole ---should be compared with mass of galaxy not galaxy itself,
Also (,and) make the previous clause seem a fluff
D - Exists ( Singular) for Black holes
E- Same as D

Hello JenniferMassey,

We hope this finds you well.

We are pleased to inform you that your elimination here is perfectly correct.

To understand the other flaws that can be used to identify the best answer choice, you can take a look at our detailed explanation for this question, here.

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

Hi GMATNinja,

Why in option C we can't consider that "the mass of" is ellipsed at the end?

Kindly explain. Many thanks in advance.

Posted from my mobile device

Think about (C) in comparison to (B).

In (B), we get the following construction: "the mass of each black hole is proportional to that of its host galaxy."

Here, it's crystal clear that "that" is a stand-in for mass, and we're comparing the mass of a black hole to the mass of the host galaxy. Makes sense.

In (C), we get: "the mass of each black hole is proportional to its host galaxy."

Now we have to play mind-reader. Did the writer mean to compare the mass of black hole to the host galaxy itself? Did the writer mean to compare the mass of one to the mass of the other, but just left off the second "mass," assuming we'd be able to figure that out?

The first interpretation is illogical. And even if we want to argue that the second interpretation is possible, there's no real clue to indicate that this was the intent, leaving it to the reader to guess. At best, it's confusing.

So no need to agonize. (B) is clear. (C) is not. Clear is better, so (B) is our answer. Simple as that.

I hope that helps!

Is answer B missing a comma before and ?

« blah blah ( independent Clause) And that + s+V ( independent Clause)

Should it not be ic+,+ and + ic

Posted from my mobile device

Hello HoustonRocks,

We hope this finds you well.

To answer your query, the presence of "that" actually means that the latter position of Option B does not form an independent clause; rather, "and" joins the two phrases "that black holes...probably exist at the core of nearly all galaxies" and "that the mass of each black hole is proportional to that of its host galaxy".

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

Got the answer right however I was wondering if 'evidence' should be singular or plural?

Thanks

Evidence is singular, always.

Are you thinking about the word for evidence in some other language? Asking because there ARE lots of languages in which some or all of the words for various classes of information/facts—e.g., the words for information, evidence, knowledge, counsel, advice, and so on—are plural.
English, however, is not one of these languages. Look at the word evidence—there's nothing about this word that suggests that it might be plural.


More generally:
On the GMAT, words that 'look singular' are singular, and words that 'look plural' are plural, unless the sentence contains direct proof of the opposite.
I'm not talking about anything complicated here... By "words that look plural" I just mean words that end in the standard plural ending "-s".

For example, the word statistics can be either singular or plural, depending on the meaning (statistics as an academic subject is singular; statistics meaning "more than one statistic / more than one data point" is plural).
On the GMAT, though, statistics will be plural (because that's what it looks like!)—unless the sentence contains actual grammatical proof that it's singular, such as agreement with a singular verb in the non-underlined section.

Words that DON'T "look plural"—such as evidence—will NEVER be plural on the GMAT.

This is really just another one of the many, many ways in which the GMAT avoids ALL 'trick questions'—a very nice feature indeed.

There's a flaw in this sentence, I think.
Without the working verb in the second part of the parallelism, which should be "is" based on this context, the whole structure is not quite right.

I've checked the source in OG (OG 2019 #792) and found that it is indeed written in this way. I have to say it's confusing.


Although this flaw is unrelated to the question itself, not in the underlined part, I found another sentence from GMATprep with the same parallel structure.
And this time, it is well written and underlined.


DmitryFarber GMATNinja RonTargetTestPrep
Sir, Could you help me understand this structure "matter is so concentrated and the pull of gravity so powerful."
Is that wrong, as I guessed at the beginning of this post. Or the missing verb is some kind of acceptable style.


Edit:
A new GMATprep example emerges, and it appears that lack of second verb could be acceptable.
I'm really confused

Well, it's in the non-underlined portion of the sentence, so the GMAT doesn't want us to worry about it at all in this case.

But the the fact that such a construction appears both here and in the underlined portion of another OA is enough to answer your question: omitting the second verb isn't necessarily a problem, and it's really just a stylistic choice to include or omit the verb. Personally, I think it sounds a little bit weird and pretentious to omit the verb in this situation, but plenty of wonderful writers would disagree with me.

Anyway, whenever you encounter something like this -- a construction that seems odd, but you're not sure whether it's definitively WRONG -- just be conservative and move on to other issues. Especially if it's something that appears in all of the answer choices, or in the non-underlined portion of the sentence.

I hope that helps!

Hey nisen20

Thank you for this excellent question. The degree of detail you've put into your analysis is remarkable. Kudos!

To add to what GMATNinja has said above, I'd like to state the following:

You must not consider either the inclusion or the exclusion of the verb a "deterministic error" in these cases. The omission of a repetitive verb in consecutive clauses is a common practice in standard English. But it remains a stylistic choice and not a hard and fast rule.

Now, sometimes, we even find the use of a comma to indicate the omission of a repetitive verb in consecutive clauses. For example:

• Jupiter is the largest planet in our solar system, and Mercury, the smallest.
• Italy is famous for her composers and musicians, France, for her chefs and philosophers, and Poland, for her mathematicians and logicians.

Commas are not always strictly necessary: you can leave them out if the sentence is perfectly clear without them:

• Italy is famous for her composers and musicians, France for her chefs and philosophers, and Poland for her mathematicians and logicians.

This is exactly what we see in the original question in this thread and the first two official questions you've shared.

Now, such omission of repetitive verbs in consecutive clauses applies even to consecutive "inverted" clauses, and this is exactly what we see in the third question you've shared:

• So dogged were Frances Perkins’ investigations of the garment industry, so persistent (was) her lobbying for wage and hour reform, that Alfred E. Smith and Franklin D. Roosevelt recruited Perkins to work within the government, rather than as a social worker.

The first two clauses are inverted, and the second clause omits the verb 'was'. However, in such cases, we generally do not use a comma to indicate the omission of the verb.

To conclude:

• Omission of the verb in consecutive clauses is a stylistic choice and neither a hard and fast rule nor a deterministic error.
• It makes the sentence more elegant and crisp, but that does not mean that repeating the verb is incorrect either.
• Sometimes, even a comma can be used to indicate the omission of a repetitive verb, but this comma is also not mandatory in straightforward clauses.
• In inverted clauses, a comma is generally not used to indicate omission of verbs.

I hope this helps improve your understanding.

Happy Learning!

Abhishek

Ref: https://www.sussex.ac.uk/informatics/pu ... ma/gapping