GMAT Tip of the Week: Come On,Commas! 3 Reasons You Should Look Forward To Commas On Sentence Correction

GMAT Tip of the WeekAdmit it – perhaps your favorite thing about the social media revolution is that you’re (or is it “your”?) almost done having to think about punctuation ever again. Hashtags don’t allow for punctuation, and with only 140 characters to express your point of view or challenge three friends to dump water on their heads, who can afford to waste a character on a comma or semicolon?

But regardless of how you feel about punctuation in your own writing, you should look forward to seeing a certain type of punctuation on GMAT Sentence Correction questions. Why?

Commas are clues.

While you’re doing Sentence Correction problems, commas can alert you to three very important Decision Points or strategic uses:

1) Commas help you identify Modifier errors.

Consider this sentence, which comes straight from the Official Guide for GMAT Review:

Architects and stonemasons, huge palace and temple clusters were built by the Maya without the benefit of the wheel or animal transport.

That comma should jump off the screen at you – when a comma appears in the first 10 words of a sentence and is underlined or touches the underlined portion, there’s an incredibly high likelihood that you’re dealing with a Modifier error in at least a couple answer choices. Even more so, if the comma is at the beginning or end of the underline, that probability creeps up to almost 100% – most modifiers are set off by commas, and the most hard-and-fast rules for modifiers apply toward the beginnings of sentences (participial and appositive modifiers get to take some liberties toward the ends of sentences), so in a case like this you should be salivating when you see that comma after the third word and touching the underline. Since “Architects and stonemasons” is a modifier here, it has to logically be able to describe the next noun, and here it cannot (palaces and temple clusters can never be architects), so you have not only eliminated A but also identified the “game” in the sentence – now you have to go find a proper modifier or continue to eliminate flawed ones.

2) Commas signal nonessential modifiers, helping you lighten your load.

What if the sentence above were changed to:

Architects and stonemasons, the most respected of early Mayan craftsmen, were built without the benefit of the wheel or animal transport.

That comma in the same place still alerts you to a modifier, but in this case “the most respected of early Mayan craftsmen” can logically modify “Architects and stonemasons.” So you can’t eliminate this sentence. But since you have identified a *valid* modifier, you have another tool at your disposal – you can ignore it! We call this the “Use It or Lose It” modifier strategy. When you see a modifier, if you don’t “Use It” to eliminate the answer choice (because the modifier is flawed) then “Lose It” – that modifier just adds extra description that isn’t totally necessary to the meaning of the sentence, so you can stop reading at the first comma and start reading again at the second, making the sentence:

Architects and stonemasons were built without the benefit…

And there you should see the mistake – logically that doesn’t work, since architects aren’t “built.” The modifier in this iteration of the sentence is there to distract you from the subject of the sentence, but by identifying commas that set apart a valid modifier, you can lift out that part of the sentence and more quickly cut to the chase.

3) Commas signify lists (which in turn need to be parallel).

Consider another sentence from the GMAT Prep Question Pack:

Displays of the aurora borealis, or “northern lights,” can heat the atmosphere over the arctic enough to affect the trajectories of ballistic missiles, induce electric currents that can cause blackouts in some areas and corrosion in north-south pipelines.

In this sentence, look at that underlined comma next to “induce.” “Induce” is a verb and is not used here as a description, so that comma-verb combination should jump out at you as a clue. This may well be setting up a list of verbs that all stem from one subject or action, like “the race requires competitors to swim in frigid waters, bike across rugged terrain, and run along challenging trails” in which the list of verbs “swim, bike, and run” all must be parallel.

Here, notice that the verb prior to “induce” is “to affect” – this should show you that the displays of the northern lights heats the atmosphere enough to do at least two things:

*affect (the trajectories)
*induce (electric currents)
*and…anything else?

That comma before “induce” should have you on a hunt for that third item in the list, preceded by the word “and” – if you can’t find it, the sentence is wrong. You can’t say “Tonight I plan to exercise, eat dinner.” It has to be “…exercise, eat dinner, and (third verb)” or “…exercise and eat dinner.” So when you see that comma before the verb, you should check to see if you’re dealing with a list, and then make sure that the list is complete (with a connector like “and” or “or” before the last item) and parallel.

Commas may be going the way of bookstores and newspapers, a bit outdated for the social media generation, but at least on GMAT Sentence Correction they’re still important. So in your question for a GMAT score that’s well above “comma” it will pay to look for the comma.

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By Brian Galvin

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