To map Earth's interior, geologists use a network of seismometers to

A, D and E: cold, dense regions and slower
Here, a reader might construe that slower is an ADJECTIVE intended to be parallel with cold and dense (both adjectives).
The intended meaning is for slower to serve as an ADVERB modifying traveling.
B and C convey this meaning more clearly by using the parallel forms most rapidly and more slowly:
MOST RAPIDLY through cold, dense regions and MORE SLOWLY through hotter rocks.
Eliminate A, D and E.

The referent for which + PLURAL VERB must be the NEAREST PRECEDING PLURAL NOUN.
B: waves that originate...which travel
Here, which travel (which + PLURAL VERB) seems to refer to waves (the nearest preceding plural noun).
As a result, that and which both have the same referent (waves).
Two different pronouns cannot have the same referent.
Eliminate B.

The correct answer is C.

Dear Friends,

Here is a detailed explanation to this question-



Choice A: In Option A, we observe a parallelism error between "rapidly traveling" and "slower"; the word "rapidly" is an adverb, while "slower" is primarily an adjective that is being used as an adverb in this case. Thus, Option A is incorrect.

Choice B: In Option B, we see a modifier error; the word "which" is preceded by a comma and a noun, meaning that "which" will refer to the noun "interior". This modification alters the meaning of the sentence by implying that "the interior" is what is traveling, rather than the "waves". Thus, Option B is incorrect.

Choice C: Option C maintains parallelism throughout the sentence. Moreover, this option avoids the modifier error found in Option B; it does so by utilizing the modifier ", traveling..." which affects the preceding action, rather than the preceding noun. Thus, Option C is correct.

Choice D: Option D repeats the parallelism error seen in Option A. Thus, Option D is incorrect.

Choice E: Option E repeats the parallelism error seen in Options A and E. Moreover, Option E is needlessly wordy as it includes a second conjunction and "that" to describe how the waves travel through the different regions. It would be more concise to apply a modifying phrase to the verb "ricochet", as this verb is a component of how the waves travel. Thus, Option E is incorrect.

Hence, C is the best answer choice.

To understand the concept of using "Which, Who, Whose, and Where on GMAT”, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team

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 the crucial part of this sentence is that the seismic waves ricochet around the interior of the Earth's crust, and in doing so travel most rapidly through cold, dense regions and more slowly through hotter rocks.

Concepts tested here: Meaning + Modifiers + Parallelism + Grammatical Construction

• Any elements linked by a conjunction ("and" in this sentence) must be parallel.
• "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma.
• If a phrase is subordinate to another in terms of importance (or sharing a cause-effect relationship), the phrases do not maintain parallelism.
• If a list contains two elements they are joined by a conjunction.

A: This answer choice fails to maintain parallelism between "most rapidly traveling through cold, dense regions" and "(traveling) slower through hotter rocks"; please remember, any elements linked by a conjunction ("and" in this sentence) must be parallel.

B: This answer choice incorrectly refers to "interior" with "which travel most rapidly...hotter rocks", illogically implying that the Earth's interior travels most rapidly through cold, dense regions and more slowly through hotter rocks; the intended meaning is that the seismic waves travel most rapidly through cold, dense regions and more slowly through hotter rocks; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma.

C: Correct. This answer choice uses the phrase "traveling most rapidly through cold, dense regions", avoiding the modification error seen in Option A and conveying the intended meaning - that the seismic waves ricochet around the interior of the Earth's crust and, as a subordinate action, travel most rapidly through cold, dense regions, and more slowly through hotter rocks. Further, Option C maintains parallelism between "most rapidly through cold, dense regions" and "more slowly through hotter rocks". Additionally, Option C correctly uses conjunction ("and" in this sentence) to join two elements in a list.

D: This answer choice alters the meaning of the sentence through the phrase "ricochet around its interior and most rapidly travel through cold, dense regions"; the parallelism between "ricochet" and "travel" incorrectly implies that the seismic waves ricochet around the interior of the Earth's crust and, as a separate and equal action, travel most rapidly through cold, dense regions, and more slowly through hotter rocks; the intended meaning is that the seismic waves ricochet around the interior of the Earth's crust and, as a subordinate action, travel most rapidly through cold, dense regions, and more slowly through hotter rocks; please remember, if a phrase is subordinate to another in terms of importance (or sharing a cause-effect relationship), the phrases do not maintain parallelism. Further, Option D incorrectly uses the "comma + conjunction ("and" in this sentence)" construction to join two elements in a list; please remember, if a list contains two elements they are joined by a conjunction.

E: This answer choice alters the meaning of the sentence through the phrase "that...ricochet around its interior and that most rapidly travel through cold, dense regions"; the parallelism between "ricochet" and "travel" incorrectly implies that the seismic waves ricochet around the interior of the Earth's crust and, as a separate and equal action, travel most rapidly through cold, dense regions, and more slowly through hotter rocks; the intended meaning is that the seismic waves ricochet around the interior of the Earth's crust and, as a subordinate action, travel most rapidly through cold, dense regions, and more slowly through hotter rocks; please remember, if a phrase is subordinate to another in terms of importance (or sharing a cause-effect relationship), the phrases do not maintain parallelism. Further, Option E fails to maintain parallelism between "travel most rapidly through cold, dense regions" and "(traveling) slower through hotter rocks"; please remember, any elements linked by a conjunction ("and" in this sentence) must be parallel.

Hence, C is the best answer choice.

To understand the concept of "Which, Who, Whose, Where", you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team

To map Earth's interior, geologists use a network of seismometers to chart seismic waves that originate in the earth's crust and ricochet around its interior, most rapidly traveling through cold, dense regions and slower through hotter rocks.

(A) interior, most rapidly traveling through cold, dense regions and slower The use of “and” tells us that we need to look out for parallelism. “Rapidly” and “slower” are not parallel. So, this can’t be the answer.

(B) interior, which travel most rapidly through cold, dense regions, and more slowly When a clause begins with “,which” it is referring to the immediately preceding non-person noun. The “, which” implies that the sentence is saying that “interior” travel rapidly.

(C) interior, traveling most rapidly through cold, dense regions and more slowly "Rapidly" and "slowly" are parallel.

(D) interior and most rapidly travel through cold, dense regions, and slower The use of “and” tells us that we need to look out for parallelism. “Rapidly” and “slower” are not parallel. So, this can’t be the answer.

(E) interior and that travel most rapidly through cold, dense regions and slower The use of “and” tells us that we need to look out for parallelism. “Rapidly” and “slower” are not parallel. So, this can’t be the answer.

- Nitha

Normally we wouldn't stack two noun modifiers together like that, regardless of whether "which" or "that" is used. In this case, since the first modifier ends in a noun ("interior"), the second modifier ends up incorrectly modifying that noun. That's one of the main reasons we're not going to do well stacking modifiers.

In theory, you could have two modifiers, one essential (using that) and the other non-essential (using which):

The book that I wrote, which comes out this summer, describes my experiences in Iran.

Note that in this case, the first modifier ends in a verb, not a noun, so there's no confusion about what the second noun is modifying.

C is not modifying the interior but it is modifying the whole preceding phrase.
the comma + ing phrase can be used to show cause and effect relationship as well as to give extra info about the preceding phrase.
Here the modifier is performing the latter part.

And between slower and more slowly we require adverb to modify travelling. So more slowly is correct

I think it's C

Slower vs more slowly - it's the latter. hence, B or C. I don't see why there should be a comma in B after 'regions', so I go with C.

To map Earth's interior, geologists use a network of seismometers to chart seismic waves that originate in the earth's crust and ricochet around its interior, most rapidly traveling through cold, dense regions and slower through hotter rocks.

A. interior, most rapidly traveling through cold, dense regions and slower
- "rapidly" is NOT // w/ "slower"

B. interior, which travel most rapidly through cold, dense regions, and more slowly
- ", which" incorrectly refers to "interior". How can interior travel rapidly?

C. interior, traveling most rapidly through cold, dense regions and more slowly
- correct as is.

D. interior and most rapidly travel through cold, dense regions, and slower
- same as "A". "rapidly" and slower" are NOT //

E. interior and that travel most rapidly through cold, dense regions and slower
- same as "A". "rapidly" and slower" are NOT //

pretty easy here once you understand that they're testing parallelism. "rapidly" and "slowly" are both adverbs that need be parallel. once you get this, you've got a 50/50 shot!

Kudos please if you find this helpful

There's a simple problem with E. It says "waves that originate AND richochet AND that travel." That looks like a mess of conjunctions and an unneeded second "that"! If we wanted to justify the last part by saying it's "that originate and ricochet" AND "that travel," we'd need to have a reason to separate that third verb out. The version in C makes much more sense. "Traveling rapidly/slowly" is what the waves do WHILE they're ricocheting, and an adverbial modifier ("traveling") is the way to express that.

As for "most rapidly/slower," that *can* be parallel. Fast and slow are funny words, in that they are used as both adjectives and adverbs. Language can be funny that way.

teaser,

"cold, dense" are coordinate adjectives that do not require conjunction between them.

Please google 'coordinate adjectives" and get the correct picture.

About B:



The simple way to eliminate choice B is for the wrong reference of the pronoun 'which". Earth's interior cannot travel and therefore the pronoun's placement next to 'interior' is a lethal flaw. As we may see, the relative pronoun cannot jump over the verb 'originate' and refer to the waves.

One point in C about the modification of the present participle preceded by a comma should be kept in mind. If there are two clauses before the comma +verbing modifier, we must be always being concerned about the subject and the action of the immediate previous clause and not the farther clause. It would not matter whether the previous clause is a relative clause or a subordinate clause. In the given context, 'geologists', the subject of the main clause, has no locus standi to be in contention with 'waves'.

Your understanding of how VERB-ing modifiers operate when they follow CLAUSE + COMMA is correct, but in this case, you've got the wrong clause. Take another look at the relevant portion:

"...geologists use a network of seismometers to chart seismic waves that originate in the earth's crust and ricochet around its interior, traveling most rapidly through cold, dense regions..."

The clause that precedes "traveling" is "that [waves] originate in the earth's crust and ricochet..." It makes perfect sense for "traveling most rapidly through cold dense regions," to provide additional context about what the waves are doing when they're ricocheting around, so (C) is fine.

The takeaway: when you see COMMA + VERB-ing, it's possible there will be multiple preceding clauses. Make sure you're evaluating the correct one.

I hope that helps!

A, D and E: cold, dense regions and slower
Here, a reader might construe that slower is an ADJECTIVE intended to be parallel with cold and dense (both adjectives).
The intended meaning is for slower to serve as an ADVERB modifying traveling.
B and C convey this meaning more clearly by using the parallel forms most rapidly and more slowly:
MOST RAPIDLY through cold, dense regions and MORE SLOWLY through hotter rocks.
Eliminate A, D and E.

The referent for which + PLURAL VERB must be the NEAREST PRECEDING PLURAL NOUN.
B: waves that originate...which travel
Here, which travel (which + PLURAL VERB) seems to refer to waves (the nearest preceding plural noun).
As a result, that and which both have the same referent (waves).
Two different pronouns cannot have the same referent.
Eliminate B.

The correct answer is C.

Here verb-ing part is modifying or defining the way seisomometers chart seismic waves. They do so by travelling through different routes in different ways.

The seismometers chart seismic waves by traveling

most rapidly through cold, dense regions and
more slowly through hotter rocks.

even if travelling is not mentioend near more slowly it is understood.

Keep in mind we need to compare like terms. In each answer, it says, "rapidly." So because there's a comparison, we need "slowly." Elim all but B & C.
C is correct because it's saying [subject] travelling most rapidly...and [implied subject] [implied verb] more slowly. I teach my clients that a common subject is like a fork, and the verbs are like the prongs. If there is a common subject we need verbs and other things to be parallel.

Regarding your first question, I think you should consider BOTH of the points you mentioned when eliminating choice (B)!

You are right that "which" doesn't always modify the preceding noun, but in this case we have an entire clause in between the "which" and the thing it should modify. That alone is a pretty strong vote against (B). And, as you said, the "which" can't possibly modify the closest noun ("interior"), since that would require using a singular verb ("travels").

But let's say we're okay with that and assume that "which" correctly modifies "waves". In that case we'd want to use a parallel structure, i.e.: "... seismic waves (1) that originate and ricochet AND (2) that travel...". Instead, choice (B) essentially gives us, "... seismic waves (1) that originate and ricochet, (2) which travel...". The use of two different relative pronouns ("that" and "which") and the lack of an "and" to link the two modifiers makes this structure confusing, at best.

So instead of looking at individual grammar points in a bubble to figure out which "rule" (B) violates the most, just recognize that the logical meaning is much clearer in choice (C).

Grammar issues are, at heart, about clarity and logic. So when comparing two choices, you always want to think about meaning. Do the differences between the two options impact the meaning? Is the meaning more clear/logical/reasonable in one option?

For more on that, check out the our SC guide for beginners, if you haven't already.

I hope that helps!

To map Earth's interior, geologists use a network of seismometers to chart seismic waves that originate in the earth's crust and ricochet around its interior, most rapidly traveling through cold, dense regions and slower through hotter rocks.

A. interior, most rapidly traveling through cold, dense regions and slower : what is most rapidly travelling thru cold? not sure move on!
B. interior, which travel most rapidly through cold, dense regions, and more slowly : interior travel? weird!
C. interior, traveling most rapidly through cold, dense regions and more slowly : travelling modifies richocheting and it says "seismeic waves richocheting by travelling through bla bla...." seems correct!
{remember two functions of ",ing" modifier 1. describe the action and should hold logical with the subject performing the same action (use "by" as shown in above example) 2. cause and effect. }
D. interior and most rapidly travel through cold, dense regions, and slower : and is wrongly used. read the sentence and youll know how it sounds. (and and and.....) no proper parallelism!
E. interior and that travel most rapidly through cold, dense regions and slower : now this "and"puts two things in parallel ..seismic waves that originate and seismic waves that travel most rapidly ...seems correct

between C and E
richocheting means something moving like a bullet ( here richochet is used as a verb) thus intended meaning is to describe that richocheting ..even if intended meaning is not clear go for other split that is C : most rapidly.. and slowly...
E : most rapidly.. and slower .
so C is describing the richocheting (verb) using "slowly" (adverb) correctly but "slower" is comparative form (adjective)
ans : C

Absolutely! And that's precisely the reason why this is not a great construct Ashmit.


Well, which pretty much always looks at only the grammatical antecedent. that is more flexible in this regard.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses "which" vs "that", its application and examples in significant detail. If you or someone is interested, PM me your email-id; I can mail the corresponding section.