Hello Everyone!
While it seems that the original question came with a pretty thorough explanation, let's see if we can figure out how you would tackle this question if you found in on the GMAT! To get started, let's look at the original question, and highlight any major differences in
orange:
Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck"—
at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.
(A)
at some time in the past our ancestors suffered an event
, greatly reducing their numbers(B)
that at some time in the past our ancestors suffered an event
that greatly reduced their numbers(C)
that sometime in the past our ancestors suffered an event
so that their numbers were greatly reduced(D)
some time in the past our ancestors suffered an event
from which their numbers were greatly reduced(E)
some time in the past, that our ancestors suffered an event
so as to reduce their numbers greatly,After a quick glance over the options, there are a couple things we can focus on:
1. at some time / that at some time / that sometime / some time
2. Their endings (intended meaning)Let's start by taking a closer look at #1 on our list: how to begin! We know that the phrase starts directly after an em dash, so we need to follow the rules concerning em dashes. In this sentence, the em dash is used to show that what follows is a more detailed explanation of a "population bottleneck." You could replace the em dash with the phrase "in other words" and it should still make sense because both the original explanation and the "rewording" of it should be parallel:
Some anthropologists believe
that the genetic homogeneity evident in the world's people is the result of a "population bottleneck"—at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.
(A)
at some time in the past our ancestors suffered an event, greatly reducing their numbers
(B)
that at some time in the past our ancestors suffered an event that greatly reduced their numbers
(C)
that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced
(D)
some time in the past our ancestors suffered an event from which their numbers were greatly reduced
(E)
some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,
We can eliminate options A, D, & E because they don't have the word "that" to create a parallel structure to the original explanation.Now that we only have 2 options to choose from, let's add in the rest of the sentence and check for other problems:
(B) Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck"—that at some time in the past our ancestors suffered an event that greatly reduced their numbers and thus our genetic variation.
This is
CORRECT! It uses parallel wording by starting both explanations with the word "that." It also uses parallel structure to list the two things that were greatly reduced: their numbers / our genetic variation. It uses the structure "greatly reduced X and Y," where X and Y were both written using parallel structure (pronoun + noun).
(C) Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck"—that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced and thus our genetic variation.
This is
INCORRECT! While it does use parallelism to start both explanations with "that," there is a parallelism problem later on:
their numbers were greatly reduced and thus our genetic variation = X was greatly reduced and Y =
NOT PARALLELTo fix it, we would have to repeat the verb:their numbers
were greatly reduced and thus our genetic variation
was greatly reduced = X was greatly reduced and Y was greatly reduced =
PARALLELThere you have it - option B is the correct choice because it uses parallel structure throughout the sentence!Don't study for the GMAT. Train for it.
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