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.
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A. which, causing plant and animal extinctions, marks
"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).
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B. which caused the plant and animal extinctions marking
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).
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C. and causing plant and animal extinctions that mark
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.
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D. an event that caused plant and animal extinctions, and it marks
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.
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E. an event that caused the plant and animal extinctions that mark
(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.
- boss, can you please explain why in option E we should not have "that marked" the end of ... ? Is it correct to have "that mark" ?