Sixty-five million years ago, according to some scientists, an asteroi

This one isn't too awful, compared to some of the QOTDs we'll inflict on you later this week. For the most part, this is a nice story about straightforward uses of "that" and "which" modifiers, with some meaning stuff thrown in.

The uses of "that" and "which" can get nastier, though. Check out last Monday's YouTube webinar for more on the various uses of "that" on the GMAT... and we'll feature the other examples from the webinar as QOTDs later this week.


"Which" can only modify "North America" here, and that makes no sense at all: "North America, which... marks the end of the geologic era"?! The placement of the "-ing" modifier doesn't seem great, either. Eliminate (A).


Again, the modifier beginning with "which" is modifying "North America" again, and that makes no sense: "North America, which caused the plant and animal extinctions..." Eliminate (B).


I'm OK with the use of "that" here, but the parallelism doesn't work. The parallelism marker "and" is followed by "causing plant and animal extinctions", and I can't find anything in the sentence that could possibly be parallel to "causing." (C) is gone.


The last part of the underlined portion makes me hesitate: "it" could refer to "event", I guess. So "...an event that caused plant and animal extinctions, and the event marks the end of the geologic era..." That's not awful, but I really don't understand why we're starting a whole new clause there, with "event" as the subject. It makes a whole lot more sense when the end of the sentence says "... marks the end of the geologic era..." function as a modifier for "extinctions" -- and that's exactly what (E) does.

Since "it" is the subject of the second clause, you could also argue that it refers back to the subject of the first clause: "an asteroid bigger than Mount Everest." But that wouldn't really make much sense, either: the asteroid marks the end of the geologic era? Hm, not so sure about that one. But either way: even if you're OK with the pronoun, (E) does a much better job of conveying the meaning of the sentence.

Incidentally, there's another version of this answer choice in the verbal guide (any edition): "an event that caused plant and animal extinctions, which marks..." Clearly, that's wrong for a different reason: "extinctions... marks" is a clear subject-verb error.

Either way, (D) is gone.


(E) has two "thats", and they're both perfectly fine. The event caused the plant and animal extinctions, and the extinctions mark the end of the geologic era. Nice and clear. (E) wins.
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first of all, i'll say that you don't really need to confuse yourself with terminology .. for most part, learning the terminology is just a waste of time

which is a noun modifier and is placed as closely to the noun it modifies as possible

in A & B which incorrectly modifies N.America

ask yourself .. what cause the extinctions? .. it was the act of the asteroid slamming into N.America that caused the extinctions
so look for a modifier that describes this act ... an event correctly defines this act

D: what does 'it' refer to?
the clause after comma is a consequence of the asteroid impact .. the use of 'and' impairs the original intent

E: here THAT may confuse you ... but it actually modifies the plant and animal extinctions ... and is an essential modifier

E is correct

In D, "an event that....extinctions" is set off by commas from the rest of the sentence and provides extra information about the event (the asteroid slammed into NA). So you should be able to remove this portion of the sentence without changing the meaning of the sentence.

Let's read D:
[Modifiers to provide context] An asteroid slammed into NA, [extra information about this event], and it marks the end...

Now ask what "it" refers to.

If you want "marks the end..." to refer to the event, then "that" must replace "it":
An event that caused X and that marks Y.

"Caused X" and "marks Y" would then become parallel constructs specifying two different effects of the same event.

In E, the position of the "the" helps one determine what "that" refers to. Everything between "the" and "that" forms a group, and the "that" refers to all the items in that group.

What if you wanted "that" to refer to just the animal extinctions? You would place "the" before "animal extinctions". The sentence might read: "...an event that caused plant extinctions and the animal extinctions that mark the end...".
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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 the crucial part of this sentence is that an asteroid bigger than Mount Everest slammed into North America, and the asteroid doing so caused the plant and animal extinctions that mark the end of the Cretaceous Period.

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

• "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma.
• Information vital to the core meaning of the sentence cannot be placed between commas.
• Information that is permanent in nature is best conveyed through the simple present tense.
• The simple past tense is used to refer to actions that concluded in the past.
• The simple present continuous tense is used refer to actions that are currently ongoing and continuous in nature.
• Present participles ("verb+ing" – “marking” in this sentence) are used to modify nouns, refer to ongoing events in any time period, and (when preceded by a comma) express cause-effect relationships.

A: This answer choice incorrectly refers to "North America" with "which...marks the end of the geologic era known as the Cretaceous Period", illogically implying that North America marks the end of the Cretaceous Period; the intended meaning is that the plant and animal extinctions caused by the asteroid slamming into North America mark the end of the Cretaceous Period; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma. Further, Option A incorrectly places information that is vital to the core meaning of the sentence - that the asteroid slamming into North America caused plant and animal extinctions - between two commas; please remember, information vital to the core meaning of the sentence cannot be placed between commas.

B: This answer choice incorrectly refers to "North America" with "which caused the...the Cretaceous Period", illogically implying that North America caused the plant and animal extinctions that mark the end of the Cretaceous Period; the intended meaning is that the action of the asteroid slamming into North America caused the plant and animal extinctions that mark the end of the Cretaceous Period; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma. Further, Option B incorrectly uses the present participle "marking" to refer to information that is permanent in nature; please remember, information that is permanent in nature is best conveyed through the simple present tense, and present participles ("verb+ing" – “marking” in this sentence) are used to modify nouns, refer to ongoing events in any time period, and (when preceded by a comma) express cause-effect relationships.

C: This answer choice alters the meaning of the sentence through the phrase "and causing plant and animal extinctions"; the construction of this phrase incorrectly implies that the asteroid slammed into North America and as a separate action caused plant and animal extinctions; the intended meaning is that the asteroid slammed into North America and, and it doing so caused plant and animal extinctions. Further, Option C incorrectly uses the simple present continuous tense verb "causing" to refer to an event that concluded in the past; please remember, the simple past tense is used to refer to actions that concluded in the past, and the simple present continuous tense is used refer to actions that are currently ongoing and continuous in nature.

D: This answer choice alters the meaning of the sentence through the phrase "and it marks the end of the geologic era known as the Cretaceous Period"; the construction of this phrase incorrectly implies that the asteroid marks the end of the Cretaceous Period; the intended meaning is that the plant and animal extinctions caused by the asteroid slamming into North America mark the end of the Cretaceous Period.

E: Correct. This answer choice uses the phrase "an event that caused the plant and animal extinctions that mark"; this phrase refers to the action of the asteroid slamming into North America, conveying the intended meaning - that the action of the asteroid slamming into North America caused the plant and animal extinctions that mark the end of the Cretaceous Period. Further, Option E correctly uses the simple past tense verb "caused" to refer to an event that concluded in the past. Moreover, Option E correctly uses the simple present tense verb "mark" to refer to information that is permanent in nature. Additionally, Option E avoids the grammatical construction error seen in Option A, as it placed no information between commas.

Hence, E is the best answer choice.

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



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



To understand the concept of "Extra Information Between Commas" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team
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extinctions that mark

that refers to extinctions. Since extinctions are plural "mark" is fine.

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.

A. which, causing plant and animal extinctions, marks
B. which caused the plant and animal extinctions marking
C. and causing plant and animal extinctions that mark
D. an event that caused plant and animal extinctions, and it marks
E. an event that caused the plant and animal extinctions that mark


Analysis:
sentence structure: Modifier, modifier, Subject( Asteroid) + modifier + verb( Slammed) + Prepositional phrase modifier ( into...) , relative clause( which..( another ing -modifier causing......)), Verb (marks) + object of the relative clause.
Error in (A): 1. which is modifying North america ilogically
2. ing- modifier inside" which" clause doesn't have anything to modify.
3. Verb " Marks" it is in Present tense.
Error in (B):
Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America ,which caused the plant and animal extinctions marking the end of the geologic era known as the Cretaceous Period.

1. "Which" clause is illogically modifying North America

Error in (C)
Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, and causing plant and animal extinctions that mark the end of the geologic era known as the Cretaceous Period.
1. Wong parallelism: An asteroid slammed, and causing plant......
would have been correct structurally if the sentence had been " An asteroid slammed and caused plant"
But still meaning wise this is wrong, because it looks like slammed and caused are two different independent event . But actually they are not.

One of the possible fixes:

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, and causing plant and animal extinctions that mark the end of the geologic era known as the Cretaceous Period

Just remove the and after comma

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, causing plant and animal extinctions that mark the end of the geologic era known as the Cretaceous Period

Error in (D):
Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America,an event that caused plant and animal extinctions, and it marks the end of the geologic era known as the Cretaceous Period.
we have an Absolute phrase(an event that caused plant and animal extinctions) trying to modifying the entire preceding clause
if we remove this Absolute phrase the sentence will be like this:

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America and it marks the end of the geologic era known as the Cretaceous Period

Now the structure became: Subject verb1 and pronoun(it) verb2
1. we need something like: Subject verb1 and verb2
2. tense error verb1 (past) and verb2 (present)
3. Meaning asteroid did not mark the end rather the event

Correct (E)

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America,an event that caused the plant and animal extinctions that mark the end of the geologic era known as the Cretaceous Period

Structure: modifier, subject+ verb, absolute phrase modifier+ relative clause modifier starting with that correctly modifies extinctions.

Still my doubt: extinctions that mark the end.......... OR extinctions that marked the end? which one would be correct

Actually more significant issue with D (even if we assume that it refers to an event) is that the usage of and lends itself to an interpretation that this event did two completely independent and unrelated things:

i) it caused plant and animal extinctions
ii) it marks the end of the geologic era known as the Cretaceous Period

But this meaning is clearly not correct because the extinctions themselves mark the end of the geologic era known as the Cretaceous Period.


Guess arguments can be made either way, but since this is an official question, it is very clear that at the very least, GMAT considers mark as acceptable, and so should we.
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Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.

A. which, causing plant and animal extinctions, marks
B. which caused the plant and animal extinctions marking
C. and causing plant and animal extinctions that mark
D. an event that caused plant and animal extinctions, and it marks
E. an event that caused the plant and animal extinctions that mark

Usage of which

which is relative pronoun and can refer to "only" nouns.

Option A and B are using "which" to refer to the full action of "asteroid slamming into NA"
Hence Option A and B are wrong.

A. which , causing plant and animal extinctions, marks
B. which caused the plant and animal extinctions marking

Verb+ing can never be a verb
verb+ing in option C "causing " can never the verb as we require an auxiliary verb such as "is/are/were/ etc" to support the verb+ing.
As option C) makes the action parallel with the usage of "and" hence we need clauses.

Absolute Phrase

Absolute phrase is of the form "Noun + Noun Modifier" can they can modify previous clause or any noun in the previous clause (doesn't require the touch rule).
Now the event -> Correctly refers to the action of slamming.
As we have event that -> So we have the form "Noun + Noun Modifier".

The problem is usage of "it" in option D). Again it should refer to extinctions logically but it is singular pronoun and is trying to refer to the plural noun.
which is wrong in D)

hence E) wins.

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.

A., which, causing plant and animal extinctions, marks --- 'Which' has no referent, present tense ' marks' is incorrect.

B., which caused the plant and animal extinctions marking -- same pronoun error as in A.

C. and causing plant and animal extinctions that mark --- a fragment

D. an event that caused plant and animal extinctions, and it marks -- no referent for the pronoun 'it'

E. an event that caused the plant and animal extinctions that mark -- correct choice. The restrictive pronoun 'that' before the plural verb 'mark' refers to the plural noun 'extinctions'.
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I had a question regarding B).

The option currently reads: which caused the plant and animal extinctions marking

If it were: which caused the plant and animal extinctions, marking

Would it have been correct? I understand that "which" is preferred to be close to the noun it is modifying and that it usually modifies a noun; but as far as I know both these conditions are not a must. So here "which" could potentially be modifying the clause, "an asteroid bigger than Mount Everest slammed into North America". "Which", as far as I am aware, can modify a clause if the context and meaning supports the usage. And similarly it can be place a bit further from what it modifies, if meaning is clear.

Further, a comma before "marking" makes it a comma -ing modifier, and the underlined portion seems to make sense.

Any thoughts?

Hi Sagar, which is a relative pronoun and hence, can never modify a clause.

Clauses have verbs and since which is a pronoun, which can only modify a noun (not a verb).

p.s. Our book EducationAisle Sentence Correction Nirvana discusses usage of which, its application and examples in significant detail. If someone is interested, PM me your email-id; I can mail the corresponding section.
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Sir, how does one identify that mark refers to 'extinctions' and not 'an event'? The primary reason for me not choosing 'E' was because i thought 'event' is the subject in this case. Can you please elaborate on this aspect. Also can you suggest some method/statergy to identify the same?

E. An event that caused the plant and animal extinctions that mark

The restrictive pronoun 'that' before the plural verb 'mark' refers to the plural noun 'extinctions.'
'That' and 'which' are relative pronouns and hence they can only antecede ta logical noun before them. Whether that logical noun is just in front or farther off is the task
1. In this connection, it may be remembered that unlike 'which,' 'that' is a restrictive pronoun and has to modify mostly only the noun just before unless it is absurd to do so.
2. Relative pronouns cannot jump over a verb (in the given case, the verb is caused) and so there is no way 'that' or 'which' can refer to the event.

The event was the collision between two cosmic bodies. But it did not mark the end of the era. What marked the end of the era were the plural extinctions. That is the reason, the singular pronoun 'it' is wrong in choice D.
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I have the same doubt as he has "Honestly, i picked up D -- an event that caused plant and animal extinctions, which marks

Here is my reasoning,
I was struggling with which marks/mark the end of XXX, either "an event" or "extinctions", eventually, i chose "an event" because i thought it is somehow redundant to say extinctions mark the end.

another question, i am not 100% sure "which" refers to extinctions or an event.
at first glance, i view which refers to extincition, but later, i thougt it should refer to an event, because that caused plant and animal extinctions is modifier of an event, cataloging the event, if i removing the modifier, the core of the phrase is an event, so which refers to an event"

Can you please explain in detail why is D wrong ?
I have my GMAT exam next month.

It would be really great if you could spare some time to help this

mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn,
@sayantanc2 VeritasPrepKarishma, Bunuel, carcass (waiting for your insights too) Please help

Thanks in advance

Take another look at (D) "an event that caused plant and animal extinctions, which marks the end of the geologic era known as the Cretaceous Period." There's no logical or grammatical way that the modifier in red can refer back to "the event." If we wanted to have two "that" or "which" modifiers describe the same noun, we'd need a conjunction such as "and" to connect them: "The event that x and that y." First, we don't have a conjunction here. Moreover, it would be asking a lot of a reader to assume that "which" somehow refers back to a noun ("event") that precedes an entire relative clause ("that caused plant and animal distinctions"). So (D) is both ungrammatical and illogical.

I hope that helps!
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A question from our sentence correction "ask me anything" thread:


Technically, I suppose that the phrase beginning with “which” could, in theory, “reach behind” the other modifier (“that caused plant and animal distinctions”), but… why the heck would we want to write the sentence that way? It’s confusing and messy. In general, you want the modifier to be as close as possible to the thing it modifies, and in this sense, (D) isn’t ideal.

Put another way, if you think that the phrase “which marks the end of the geologic era” also modifies “an event”, then we would have two different modifiers for “an event”:

1. “that caused plant and animal extinctions”
2. “which marks the end of the geologic era…”

So if we’re saying that both of these modify an “event”, then they need to be parallel to each other. So something like “an event that caused plant and animal distinctions and that marks the end of the geologic era…” would be much, much clearer.

(E) avoids those problems entirely. The first modifier (“that caused the plant and animal extinctions”) is right next to the thing it modifies (“an event). So is the second modifier (“that mark the end of the geologic era” modifies “the plant and animal extinctions”). So the modifiers are much, much clearer than in (D).

I hope this helps!
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GMATNinja EXPERT
in option "E" that is a singular pronoun referring to plural "Extinctions" isnt it incorrect.

or is "that" acting as a modifier ?
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The whole sentence deals with the past,
The end of the sentence should be marked(past tense) how could it be just mark?

Hi Anirudddh,

A case can be made for the past tense marked, but we'll need to look at the intended meaning to see why this sentence uses the present tense mark.

...the plant and animal extinctions that mark the end of the geologic era known as the Cretaceous Period.

The that mark... is used to describe the plant and animal extinctions. These extinctions still "mark" the end of the Cretaceous Period. That's why the sentence uses the present tense mark instead of the past tense marked. If we use extinctions that marked the end of the Cretaceous Period, a reader might end up thinking that the extinctions no longer mark the end of the Cretaceous Period.
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