Hello Everyone!
Let's tackle this question, one thing at a time, and narrow down our options quickly so we know how to answer questions like this when they pop up on the GMAT! To begin, let's take a quick look at the question and highlight any major differences between the options in
orange:
Lacking information about energy use, people tend to overestimate the amount of energy used by
equipment, such as lights, that are visible and must be turned on and off and underestimate that used by unobtrusive equipment, such as water heaters.
(A)
equipment, such as lights,
that are visible and must be turned on and off and underestimate
that(B)
equipment, such as lights,
that are visible and must be turned on and off and underestimate
it when(C)
equipment, such as lights,
that is visible and must be turned on and off and underestimate
it when(D)
visible equipment, such as lights,
that must be turned on and off and underestimate
that(E)
visible equipment, such as lights,
that must be turned on and off and underestimate
it whenAfter a quick glance over the options, we have a few key differences to focus on to help narrow down our choices:
1. equipment vs. visible equipment
2. that / that are visible / that is visible
3. that vs. it whenLet's start with #1 & #2 on our list because they both deal with the same grammar issue: concision/wordiness. The GMAT prefers concise, clear language whenever possible, so we need to determine which phrasing option is the clearest and most concise. The easiest way to do this is to take out the phrase "such as lights," since it's only there to trip us up:
equipment...that are visible =
WRONG = This is both overly wordy AND a subject-verb agreement problem. Equipment is a singular word, so we can't use a plural verb "are."
equipment...that is visible =
WRONG = While this option fixes the subject-verb agreement problem, it's still not the most concise option.
visible equipment =
CORRECT = This conveys the same meaning as "equipment that is visible" in half as many words! This is our choice!
We can eliminate options A, B, & C because they are not concise and/or have subject-verb agreement problems.Now that we have it narrowed down to only 2 options, let's tackle #3 on our list - that vs. it when - which is an issue of both pronouns & parallelism! To make potential problems easier to spot, let's add back in the non-underlined portions of the sentence.
(D) Lacking information about energy use, people tend to overestimate the amount of energy used by
visible equipment, such as lights, that must be turned on and off and underestimate that used by unobtrusive equipment, such as water heaters.
This is the
CORRECT option because the pronoun "that" is clearly referring back to "the amount of energy." If you were to replace the word "that" with "the amount of energy," this would still make perfect sense!
Also, if we replace the pronoun with the phrase it's referring back to, the 2 actions are parallel:
overestimate the amount of
energy used by visible equipment
underestimate the amount of
energy used by unobtrusive equipment
(E) Lacking information about energy use, people tend to overestimate the amount of energy used by
visible equipment, such as lights, that must be turned on and off and underestimate it when used by unobtrusive equipment, such as water heaters.
This is
INCORRECT for a couple reasons. First, the pronoun "it" isn't clearly referring back to "the amount of energy" as clearly as in option D. Even if we replace the pronoun "it" with "the amount of energy," we also have a parallelism problem! There are 2 actions people are doing in this sentence:
overestimate the amount of energy
used by visible equipment
underestimate the amount of energy
used when by unobtrusive equipment
Since these two actions aren't written using parallel construction, we have to toss this one out!
There you have it - option D is the correct choice! By finding the splits among our 5 options, we were able to eliminate several incorrect choices quickly, leaving us more time to focus on the more nuanced grammar problems at hand!
Don't study for the GMAT. Train for it.
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