Source: Official Guide for the GMAT 13th Ed. Sentence Correction; #81 Official Guide for the GMAT 2015 14th Ed. Sentence Correction; #81


Fossils of the arm of a sloth

Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of the Greater Antilles Islands.

3 Explanations


Felix Manan

Hi, can I eliminate choice C based off the pronoun 'this'? When doing this problem I completely blanked out of the S-V 'was', so eliminated C on the basis of wrong usage of the pronoun 'this'. Thanks!

Apr 6, 2018 • Comment

David Recine, Magoosh Tutor

Actually, if "this" were the only split in an answer choice, there would be know problem. "It" and "this" are both acceptable singular pronouns here.

You are correct, however, to feel as if "was" created a problem. The issue here is parallel structure. In choice C, the sentence has two verb phrases separated by a comma, "was found..." and "was dated...." So you would expect the next phrase, following the comma at the end of "was dated..." would also be a verb phrase, continuing a list of actions. Instead, the sentence abruptly shifts back to a pronoun-verb structure.

This significant violation of parallel structure is confusing, so confusing that it's understandable for you to suddenly feel confused about what "this" might refer to. In that sense "this" indicated the structure was wrong, as the next phrase after "was dated..." should have been an additional verb phrase. Or the sentence shouldn't have had two verb phrases leading up to "this."

I hope that helps, but if you have a follow-up comment, feel free to post it. :)

Apr 12, 2018 • Reply



Hi. Can we eliminate the choices A,C, & E based on idiom "known mammal on" rather than "known mammal of".
I found one more reason to eliminate choice C. "sloth that was found in Puerto Rico in 1991". Here that clause refers to fossils, so the verb should be "were found". Can you please clarify ..
Thank you

Jan 6, 2017 • Comment


Hi Dino,

1. We cannot eliminate choices based on "mammal on" vs. "mammal of."
2. Yes, (C) incorrectly implies that it was the sloth that was found and not the fossils. Note that this is the first split that the Mike addresses, eliminating B C and E for singular verbs.

Jan 8, 2017 • Reply


Gravatar Mike McGarry, Magoosh Tutor

May 23, 2013 • Comment

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