Recent findings lend strong support to the theory that a black hole li

I am responding to a private message from venmic. I am happy to elaborate on this.

Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies estimated to exist in the universe.
(A) that a black hole lies at the center of the Milky Way and of
(B) that a black hole lies at the Milky Way’s center and
(C) that there is a black hole lying at the Milky Way’s center and
(D) of a black hole lying at the Milky Way’s center and
(E) of a black hole that lies at the center of the Milky Way and of

Rather that pick through each answer one at a time, let's attack this strategically, looking at splits. See this blog for more on this strategy:
https://magoosh.com/gmat/2012/gmat-sente ... trategies/

The first split is "that" vs. "of" at the very beginning. The phrase "a theory that A did B" is idiomatically correct. The phrase "a theory of A doing B" is inferior --- this construction will not be correct on the GMAT. Right away, (D) & (E) are out.

The phrase "a black hole lies ...." is active and direct, just what the GMAT likes --- we see this in (A) & (B). Meanwhile, (C) has the abominably indirect monstrosity "there is a black hole lying ...." On the GMAT SC, any time you have a choice of "[noun] [verb]" vs. "there is a [noun] [participle]", then every single time, the first will be correct and the second will be wrong. Here, we can eliminate (C) on these grounds.

Finally, we have the complex parallel construction at the end of the sentence:

....lies at the center
// of the Milky Way
and
// of many of the 100 billion other galaxies estimated to exist in the universe.

We need these to prepositions in parallel --- we are talking about something at the center of both the Milky Way and other galaxies. That means we must construct the first part in parallel ---- so "Milky Way's center" is wrong because it violates the parallelism. We need "of the Milky Way and of" at the end of the underlined section, to complete the parallelism correct. Only (A) & (E) do this correctly, but we have already eliminated (E) for other reasons.

This leaves (A) as the only possible answer.

Does this make sense?

Mike
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Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies estimated to exist in the universe.

We featured this thing in our latest YouTube webinar on parallelism and meaning, but… well, you’ll have to sift through an hourlong video to find the explanation in there. So here’s the quicker, written version that you could print out and post on your office wall. Or, um… something.


“And” is our parallelism trigger, and it’s followed by the prepositional phrase “of many of the other…” So here’s what the parallelism looks like: “Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies…”

Does that actually make sense? Sure: “recent findings lend support to the theory that a black hole lies at the center… of many of the 100 billion other galaxies…” Let’s keep (A).


If we do the same thing that we did in (A), we have problems.

The parallelism trigger “and” is followed by the noun “many of the 100 billion other galaxies.” I guess that’s parallel to the noun “the Milky Way’s center”?

So we’d have “Recent findings lend strong support to the theory that a black hole lies at the Milky Way’s center and many of the 100 billion other galaxies…”

That makes no sense. The “stem” – the part of the sentence that immediate precedes the parallel list – just doesn’t work with the second item in the list: “Recent findings lend strong support to the theory that a black hole lies at… many of the 100 billion other galaxies…”

So (B) is out.


(C) has basically the same error as (B): “Recent findings lend strong support to the theory that there is a black hole lying at the Milky Way’s center and many of the 100 billion other galaxies…”

Again, that “stem” – “recent findings lend strong support to the theory that there is a black hole lying at” – makes no sense with the second item in the list. We’d have: “Recent findings lend strong support to the theory that there is a black hole lying at… many of the 100 billion other galaxies…”

(C) is gone, too.


(D) basically has the same problem as (B) and (C). “And” is still followed by the same noun, “many of the 100 billion other galaxies. And that still doesn’t make any sense: “Recent findings lend strong support to the theory of a black hole lying at… many of the 100 billion other galaxies…”

Plus, I’m not sure that it makes a whole lot of sense to say “the theory of a black hole lying at the Milky Way’s center.” The phrase “the theory of _____” works if you can summarize that theory as a single noun: “the theory of relativity” or “the theory of evolution”, for example. But “the theory of a black hole”? I’m not so sure about that. “… the theory that a black hole lies at the center of the galaxy…” makes much more sense.

And if you don’t buy anything I wrote in that last paragraph, that’s cool for now. The parallelism issue still wipes out (D).


So the parallelism is fine here, since it’s exactly the same as in (A). So what’s the only real difference between (A) and (E)? It’s that goofy difference between “the theory of a black hole that lies…” and “the theory that a black hole lies…” And the latter makes more sense.

If you picked (E), that’s not terrible. But given the choice, (A) is better.
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Dear Friends,

Here is a detailed explanation to this question-

Meaning is crucial to solving this problem:
Understanding the intended meaning is key to solving this question; the intended meaning of this sentence is that recent findings strongly support the theory that a black hole lies at the center of the Milky Way, and a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe.

Concepts tested here: Meaning + Tenses + Awkwardness/Redundancy

• Statements of universal fact are best conveyed through the simple present tense.

A: Correct. The sentence formed by this answer choice uses the phrase "lies at...(the center) of many of the 100...universe", conveying the intended meaning - that a black hole lies at the center of the Milky Way, and a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe. Moreover, Option A uses the phrase "theory that a black hole", conveying the intended meaning - that recent findings strongly support the theory about a black hole. Further, Option A correctly uses the simple present tense verb "lies" to refer to a statement of universal fact. Additionally, Option A is free of any awkwardness or redundancy.

B: The sentence formed by this answer choice alters the meaning of the sentence through the phrase "lies at...many of the 100...universe"; the construction of this phrase leads to an incoherent meaning; the intended meaning is that a black hole lies at the center of the Milky Way, and a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe. Further, Option B uses the needlessly indirect construction "Milky Way's center", leading to awkwardness.

C: The sentence formed by this answer choice alters the meaning of the sentence through the phrase "lying at...many of the 100...universe"; the construction of this phrase leads to an incoherent meaning; the intended meaning is that a black hole lies at the center of the Milky Way, and a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe. Further, Option C incorrectly uses the present participle ("verb+ing" - "lying" in this sentence) to refer to a statement of universal fact; please remember, statements of universal fact are best conveyed through the simple present tense. Additionally, Option C uses the needlessly wordy clause "there is a black hole" and the needlessly indirect construction "Milky Way's center", leading to awkwardness and redundancy.

D: The sentence formed by this answer choice alters the meaning of the sentence through the phrase "lying at...many of the 100...universe"; the construction of this phrase leads to an incoherent meaning; the intended meaning is that a black hole lies at the center of the Milky Way, and a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe. Moreover, Option D further alters the meaning of the sentence through the phrase "theory of a black hole"; the construction of this phrase illogically implies that recent findings strongly support the theory belonging to a black hole; the intended meaning is that recent findings strongly support the theory about a black hole. Further, Option D incorrectly uses the present participle ("verb+ing" - "lying" in this sentence) to refer to a statement of universal fact; please remember, statements of universal fact are best conveyed through the simple present tense. Additionally, Option D uses the needlessly indirect construction "Milky Way's center", leading to awkwardness.

E: This answer choice alters the meaning of the sentence through the phrase "theory of a black hole"; the construction of this phrase illogically implies that recent findings strongly support the theory belonging to a black hole; the intended meaning is that recent findings strongly support the theory about a black hole.

Hence, A is the best answer choice.

To understand the concept of "Simple Tenses" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team
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D & E out - Meaning changed

C out - passive voice

B can be elimiated cause the first part of the sentece that says 'that a black hole lies at the Milky Way’s center' is perfect but the second half ' Milky Way and of many of the 100 billion other galaxies' tends to change the meaning.

Lets simplify this -
A - black hole lies at the center of X and of Y
B - Black hole lies at the X's center and Y

A can be selected as a better bet.

Please post the OA.

lets say phrase "A" is "the Milky way"
and phrase "B" is "many of the 100 billion other galaxies estimated to exist in the universe"

then the whole sentence takes the form:

Recent findings lend strong support to the theory that a black hole lies at the center of "A" and of "B".

which means" that a black whole exist at the center of "A" and at the center of "B"."

because we can omit the repeating words the sentence becomes:
"that a black hole exists at the center of "A" and of "B"."

Hence the answer is A.

A. that a black hole lies at the center of the Milky Way and of------ best answer maintaining //ism

B. that a black hole lies at the Milky Way’s center and ----- the dangling phrase after the fanboy ‘and’ does not go in tandem with the clause before the conjunction

C. that there is a black hole lying at the Milky Way’s center and ------same non-//ism as in B

D. of a black hole lying at the Milky Way’s center and --- reported findings are best introduced by a relative clause using - that -use of prepositional phrase of a black hole is unidiomatic

E. of a black hole that lies at the center of the Milky Way and of --- same mistake as in D
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I completely agree with the reasons on why options B, C, D, and E are incorrect. However, I am unable to understand the original sentence itself.

If the sentence were "Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies.", I would have agreed that the parallelism is maintained (thought I would never understand how one black hole can lie at the center of the Milky Way and at the center of many of the 100 billion other galaxies at the same time -- each of the galaxies can have a separate black hole of its own -- presence of "a" before "black hole" has created an absurd theory!).

However, the original sentence structure is:
..... a BH lies at the center of the X and of Y estimated to exist in the universe.
What is "estimated to exist in the universe" -- answer is "100 billion other galaxies" which is a part of Y. Thus "the Milky Way" is not parallel to "many of the 100 billion other galaxies estimated to exist in the universe".

I am not able to find any sensible meaning of the sentence. Any help on this will be appreciated.

I tried to find the source of the question, but could not find anywhere. I doubt whether this question is from any reputable source and worth brainstorming!

Doe 007: I think you got the parsing of the A wrongly. Of X and Y is limited to -of the Milky Way(X) and -of the many other galaxies(Y) - . Whether it is 100 billion or 1000 billion is an inessential factor, since it is not what the text is converging on. On the contrary, the existence of a black hole is the heart of the finding. So, at the centre of the Milky Way and at the centre of the many of the galaxies are //, IMO.

Secondly, I feel that the text is trying to say that at the centre of each of these many galaxies (It is just many galaxies and not all galaxies) lies a black hole of its own. So, the suspicion whether all galaxies have a common hole may be a high inference.
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Dear doe007,

Consider the sentence ---
I would like to drive the car of my neighbor and the car of each one of his friends.
Admittedly, not a gem of rhetoric, but grammatically correct. Well, the underlined cars are in parallel, and in parallel, we are allowed to drop common elements, which omission would shorten the sentence to
I would like to drive the car of my neighbor and of each one of his friends.
This sentence, slightly better though still not ideal, is also grammatically correct. Notice, this sentence in no way implies that there is only one car, shared by neighbor & friends alike ---- rather, it quite clearly implies: my neighbor has one car, and each one of his friends has one car, and I want to drive all these cars (presumably not all at once).

Similarly, with the sentence:
Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies.
A perfectly good, perfectly clear sentence, both grammatically and logically correct. Consider the expanded version -----
Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and that a black hole lies at the center of many of the 100 billion other galaxies.
This version is far less economical, and therefore more awkward and clunky, but it makes more explicit the parallelism. This sentence says there is "a black hole" at the center of the Milky Way, and if we went to interview every other galaxy in the Universe (all 10^11 of them, admittedly, a large task!), then if we asked the spokesman of each galaxy, "Does your galaxy have a black hole at its center", the answer for the majority would be "Yes, we have a black hole at the center of our galaxy." The word "each" might have made this a shade more clear, but really it's perfectly clear from both versions above. The fact that "a black hole at the center" is a condition true for the majority of galaxies in now way implies that it is the same black hole. You are not reading the parallelism properly.

Does all this make sense?
Mike
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Hi Mike, thanks for your comment. I missed your post before!


"The car" means only one specific car. This sentence might be correct colloquially but not grammatically.



As long as the sentence is like this, it is ok. But the part "estimated to exist in the universe" is dangling awkwardly.

Dear doe007,
I am gong to play Devil's Advocate with you, partially because I believe I am right, but more because I don't want you to get anything like this wrong on the real GMAT. This is very important stuff.

It is absolutely true that we can eliminate common repeated words in parallel structure without changing the meaning. That is a fundamental and incontestable principle in GMAT grammar.

Consider this sentence:
(a) Last summer, I visited the Ben & Jerry's shop in Brattleboro and the Ben & Jerry's shop in Burlington.
That's a perfectly correct sentence, grammatically and logically, although rhetorically it has some issues because it's too wordy.
From the GMAT's point of view, an improvement would be:
(b) Last summer, I visited the Ben & Jerry's shop in Brattleboro and in Burlington.
Obviously, there's not one single ice-cream shop that is simultaneously in two different cities, nor does this sentence imply this. If you want to say sentence (b) is wrong, you have to say that sentence (a) is wrong also, because by the well-established parallelism rule, they are entirely equivalent.

It's true, for clarity, one might add some kind of separating words .....
(c) Last summer, I visited the Ben & Jerry's in Brattleboro and also in Burlington.
(d) Last summer, I visited the Ben & Jerry's in Brattleboro and two weeks later, in Burlington.
That may enhance the clarity, but they are not necessary for the fundamental meaning.

I have chosen to prolong this discussion with you because parallelism is so supremely important on the GMAT SC, and understanding all the subtleties related to parallelism, including everything about what words we can omit, is absolutely crucial to SC success.

Does all this make sense?
Mike
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Dear Mike,
Thank you for the insightful reply. Please understand that I have no problem in my understanding on removing common repeated words and I completely agree with your assertions. Also, the examples in your last post are correct.

However, I have a little problem to understand how can a specific object (e.g., the car) can refer to many different objects. Can "the car" mean Civic of Sam, Corolla of Tracy, Santro of John, Murano of Laura, and Mustang of Harry at the same time?

I have the biggest problem in considering the original sentence of this topic as a grammatically correct sentence because of the dangling portion at the end and so far I didn't hear anything from anybody.

As I mentioned before, I could not find source of the question from anywhere and I seriously doubt if brainstorming on this question is worth!

Dear doe007,
Consider this sentence.
I have great appreciation for the car of each one of my five friends.
In that sentence, there's no problem with the words "the car" standing in for the Civic of Sam, the Corolla of Tracy, the Santro of John, the Murano of Laura, and the Mustang of Harry all at once. The word "each" forces the "one for each"' reading of the sentence.

Admittedly, the word "each" goes a long way toward clarifying that the words "the car" are plural in content and distributed over a group. Also, admittedly, without the word "each", this particular sentence would be ambiguous.
I have great appreciation for the car of my five friends.
Hmm. Now, it is possible for five people to own a single car --- the "one for all" reading ---- or it is possible that each friend owns her or his own car --- the "one for each" reading --- and the speaker admires all five. Notice ----- it's not that the former is automatically the correct reading. Either reading is perfectly acceptable because the sentence is ambiguous.

Now, back to our famous sentence.
Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies estimated to exist in the universe.
To simplify things --- there's no problem with the single black hole at the center of the Milky way, so for clarity, let's eliminate that.
Recent findings lend strong support to the theory that a black hole lies at the center of many of the 100 billion other galaxies estimated to exist in the universe.
Now, both "black hole" and "center" are singular, and that fine. Here, there is absolutely no ambiguity that there could be just one galactic center with one black hole for all 100 billion galaxies --- that's crazy! Because that reading, the "one for all" reading, is simply impossible, this forces us to take the "one for each" reading as the correct reading.

I believe you are assuming, if the word "each" is not explicitly present, that the "one for all" is the only possible reading. I assert, that in cases such as this, we need to examine both the "one for all" and "one for each" readings. Most typically, the GMAT will make everything explicitly clear, either in the wording or the context, so only one of these is possible. Here, the context of the question makes clear which reading we must pick.

I don't know the source for this question either, and often that does make me suspicious, but I think it's a good question.

Does all this make sense?
Mike
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Dear Mike, I appreciate your effort and time spend on one single conversation. Your expert comments helped me to correct some of my concepts at different times. Here, please allow me to make my points little more clear for the last time.

It is ok to say:
Last week, I visited the museum in Italy.
Last week, I visited the museum in Italy and in Germany.
Last week, I visited the museum in Italy and the museums in Germany, France, and Belgium.
I want to drive each of the cars of George and Bill.

However, it is not ok to say:
Last week, I visited the museum in Italy and the museum in Germany, France, and Belgium.
Last week, I visited the museum in Italy and in 5 other countries.

The point here is, the same common word cannot refer to singular noun and plural noun (or the sense of plural) at the same time.

For this reason, I conveyed that the sentence "I would like to drive the car of my neighbor and of each one of his friends." is incorrect
But, the following sentences of your examples are grammatically correct.
Last summer, I visited the Ben & Jerry's shop in Brattleboro and in Burlington.
I have great appreciation for the car of each one of my five friends.
I have great appreciation for the car of my five friends.


The example shown here is ambiguous (as you said) at most, but it is grammatically correct as I mentioned above.


Now, back to the original sentence: Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies estimated to exist in the universe.

Structure of the original sentence is:
..... a BH lies at the center of X and of Y estimated to exist in the universe.

If the sentence were as follows, I would have agreed that the parallel structure was maintained.
..... a BH lies at the center of X and of Y.
Here Y = "many of the 100 billion other galaxies"
To maintain the parallelism, we cannot break down "many of the 100 billion other galaxies" into two parts.

With reference to the original sentence:
What is "estimated to exist in the universe"? -- the answer is "100 billion other galaxies". This makes "100 billion other galaxies estimated to exist in the universe" one indivisible phrase.

Now see, we have two indivisible parts "many of the 100 billion other galaxies" and "100 billion other galaxies estimated to exist in the universe", and there is a overlap between these two parts. This situation creates the following two alternatives for us to consider:
1) Parallelism prevails: "the Milky Way" is parallel to "many of the 100 billion other galaxies", and "estimated to exist in the universe" is dangling after the parallel parts.
2) Modification prevails: "100 billion other galaxies estimated to exist in the universe" is indivisible. In that case, "the Milky Way" is not parallel to "many of the 100 billion other galaxies estimated to exist in the universe" in the perfect sense.

As "estimated to exist in the universe" is in non-underlined part, we need to treat second scenario above as our case.


Now at this point, I see that we may not agree on the same point and it is ok to leave the matter if you wish so.

Dear doe007,
With all due respect, it seems to me there's an inconsistency between what you say and sentence #2 ---- if #2 is correct, then there's no reason that #6 shouldn't be correct.
The phrasing "the museum in Italy" sounds a little funny to me, only because there are so many museums in Italy you can't swing a dead cat without hitting one. I'm going to change "museum" to "parliament building", which presumably is something unique in each country. Then, I would assert
(7) Last week, I visited the parliament building in Italy.
(8) Last week, I visited the parliament building in Italy and in Germany.
(9) Last week, I visited the parliament building in Italy, in Germany, in France, and in Spain.
(10) Last week, I visited the parliament building in Italy and in three other countries.
(11) Last week, I visited the parliament building in Italy and in twenty other countries.
I'm sure we both agree #7 is correct. If you accept #2 above as correct, then you would have to accept #8 as correct, and probably #9 as correct as well. But #10 is just a more concise way to say #9, so if #9 is correct, how can #10 not be correct? Finally, once we accept that a number is correct, then it is immaterial what number it is, so #11 would have to be correct also. I would assert all five are correct. I would be very curious to know where you think the correct sentences end and what you use as your criterion. Strictly, if using a singular for multiple referents is always incorrect, then not only #8-11 would be incorrect, but also your #2. If you allow #2, I think you have to allow all the rest. What do you think?


Hmm, #15 now strikes me as way too ambiguous, though grammatically correct. I don't understand your criterion --- if you think #13 & #14 are correct, how can you say #12 is incorrect? The words "each one" indicates a singular individual --- indefinite, but singular. Therefore, it is of the form
[singular object]"of"[singular individual]"and of"[singular individual]
either to say
(16) .... the car of Lydia and of Hilda ....
or
(17) .... the car of Lydia and of each one of her 27 friends ....
If you allow #16, there's no reason to reject #17.

I admit, this question is not ideal, but you seem to have it in for this question. The conflict you spell out between parallelism and modification seems entirely non-existent to me.

Strictly, the parallelism is between "of the Milky Way" and "of many". Here, we get into an issue that MGMAT likes to call "subgroup modifiers." The latter term, "of many", makes no sense without making clear the larger group.
"of the Milky Way"//"of many of the 100 billion other galaxies"
That's the parallelism. Now, as it happens, the second term of the parallelism has modifier, even though the first one doesn't. This is 100% legal, and appears in correct answers in the GMAT OG.

For example, consider OG13 SC #110 --- here's the OA, choice (C):
(C) Published in Harlem, the Messenger was owned and edited by two young journalists, A. Philip Randolph, who would later make his reputation as a labor leader, and Chandler Owen.
The two individuals named, A. Philip Randolph and Chandler Owen, are in parallel, and only the first one has modifying clause. There's absolutely no problem with that.

Does all this make sense?
Mike
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Hi Guys,

I'm confused between A and B. Though I understood the explanation for A, here's my take on B.

Recent findings lend strong support to the theory that
1. a black hole lies at the Milky Way’s center
and
2. many of the 100 billion other galaxies estimated to exist in the universe.

Doesn't this also makes sense?

mikemcgarry daagh souvik101990

Dear sannidhya,
I'm happy to respond. There are many extra words in this sentence, and these extra words make the grammar hard to discern. Let's simplify.

...lie at the center of the Milky Way and of other galaxies. = correct: this is essentially what (A) has

...lie at the Milky Way's center and other galaxies. = this is essentially what (B) has

This latter construction is a logical failure. Where do the black holes lie?
(1) at the Milky Way's center = yes, that's fine
(2) at other galaxies = this is the problem

First of all, it's unidiomatic to say at other galaxies. Furthermore, it's logically incorrect: the black holes are in the centers of the other galaxies. Choice (B) changes the meaning and says this incorrect meaning in an idiomatically incorrect way. In other words, (B) is a disaster.

One important strategy for interpreting GMAT SC is what is some times called removing fluff. Often we can pare away extra detail and extra descriptive phrases, and this allows us to see the underlying grammatical relationships.

Does all this make sense?
Mike
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Hi mike,

I'm glad you responded.

However, I'm saying what if there are two findings.

1. black hole and where it lies
2. 100 billion other galaxies

Dear sannidhya,
I'm happy to respond again. My friend, with all due respect, I must tell you that you are misunderstanding the meaning of this sentence. Meaning trumps grammar. If a student doesn't understand the meaning of the sentence, then it makes it much harder for the student to understand the grammar of the sentence, because grammar depends on meaning, and the GMAT SC is as much about meaning as it is about grammar.

Here is the question again:
Recent findings lend strong support to the theory that a black hole lies at the center of the Milky Way and of many of the 100 billion other galaxies estimated to exist in the universe.
A. that a black hole lies at the center of the Milky Way and of
B. that a black hole lies at the Milky Way’s center and
C. that there is a black hole lying at the Milky Way’s center and
D. of a black hole lying at the Milky Way’s center and
E. of a black hole that lies at the center of the Milky Way and of

This sentence about a scientific theory, and this theory posits two things. The first point, as you correctly surmise, is that a black hole is at the center of our own galaxy, the Milky Way galaxy. The second point is NOT simply the existence of the other galaxies. This theory is NOT about the discovery of other galaxies. The second point is that a black hole exists at the center of each one of the billions of other galaxies. In other words, this is
. . . the theory that that a black hole lies at the center of the Milky Way galaxy and that a black hole also lies at the center of many of the 100 billion other galaxies estimated to exist in the universe.
That is factually what the sentence is saying, but that version is way too wordy. There are far too many words repeated in the parallel structure. We need to omit repeated words. See:
https://magoosh.com/gmat/2013/dropping-c ... -the-gmat/
We can shorten that to:
. . . the theory that a black hole lies at the center of the Milky Way and of the 100 billion other galaxies estimated to exist in the universe.
This is the OA, (A). Notice the repeated preposition "of" marks the parallelism.

Part of concision is dropping common words from the second branch of parallelism. It's always tricky to read a sentence in which these common words already have been dropped and to infer them as part of the meaning, but this is precisely what the GMAT SC asks students to do.

Does all this make sense?
Mike
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