This week, we’re going to analyze a particular GMATPrep® Sentence Correction question.

First, set your timer for 1 minute and 15 seconds and try the problem!

The Achaemenid empire of Persia reached the Indus Valley in the fifth century B.C., bringing the Aramaic script with it, from which was derived both northern and southern Indian alphabets.

A) the Aramaic script with it, from which was derived both northern and
B) the Aramaic script with it, and from which deriving both the northern and the
C) with it the Aramaic script, from which derive both the northern and the
D) with it the Aramaic script, from which derives both northern and
E) with it the Aramaic script, and deriving from it both the northern and

Okay, have you got your answer? Now, let’s dive into this thing! Was everything okay in the original sentence or do you want to examine anything further?

On this one, perhaps the “, from which” in the original sentence caught your eye. This marker signifies a noun modifier. Noun modifiers are supposed to modify the closest main noun; in this case, that means the noun before the comma. That noun is the pronoun “it.” So, what is “it” referring to?

“It” is referring to the empire. So the noun modifier is telling us “the empire, from which was derived <some other alphabet>. Can an alphabet be derived from an empire? Figuratively, perhaps, but not literally. Literally, one alphabet is derived from another alphabet – so the sentence should convey that meaning.

So, we’ve found an error in the original sentence, and we can immediately cross off choice A. Next, let’s scan the remaining answers to see whether we can reuse our new-found knowledge. Do any of the other choices repeat the error that we just found?

Answers C and D have “script, from which,” so they both fix that problem. Answers B and E change things up a bit – they introduce an “and” after the comma, so we no longer have a straight noun modifier marker.

Now, each person has to make a choice: do you want to try to figure out what’s happening with these new “and” markers in B and E? Or do you want to try to find something else? There isn’t one right answer to this question; it just depends upon your strengths and weaknesses. In this case, let’s examine B and E further.

B says “it, and from which deriving…” The “and” is a parallelism marker: X and Y. If this choice is correct, then, it should have some X and Y components that can be made parallel. Right after the “and,” we have the “from which” modifier marker, so this is the start of the Y component of the “X and Y” parallelism structure. What is the X? Ah, there’s the problem! We don’t have a parallel noun-modifier X component before the “and.” Eliminate B.

We know already that E also introduced an “and” at this point in the sentence, so let’s see if we can reuse our work from B on E. This time, we have “script, and deriving…” The word “deriving” is the start of our Y component; what is the parallel X component? Perhaps it’s the word “bringing” from the non-underlined portion? Let’s test it out.

The Empire reached the Valley, bringing with it <a script>, and deriving from it <some alphabets>. These “comma –ing” structures are adverbial modifiers, which modify the preceding clause (subject and verb). In addition, the parallelism sets up certain expectations; for instance, when using the same pronoun in the same position in two parallel structures, the expectation is that the pronoun refers to the same noun both times. What does the first “it” refer to? Does the second “it” refer to the same noun?

No. The first “it” refers to the “empire,” while the second “it” refers to the “script.” Further, parallel structures should be able to be used independently to complete a sentence. We should be able to say: (1)The Empire reached the Valley, bringing with it a script. (2) The Empire reached the valley, deriving from it some alphabets. What does the “it” refer to in the second sentence? The valley? The empire? Neither one makes sense. Eliminate E.

So now we’ve narrowed it down to C and D, both of which use a “script, from which” construction. Scan the two choices vertically, comparing parts until you find any differences. There are only two: one uses the singular “derives” while the other uses the plural “derive,” and one includes “the” in front of both northern and southern while the other does not use “the” for either one.

The derives / derive split seems as though it should be straightforward – we just have to determine whether we need the verb to be singular or plural, right? Great. So, what is the subject that matches with this verb?

Ask yourself who or what is doing the action – what derives from what? The script derives from the alphabets? Or the alphabets derive from the script? The original sentence describes the latter scenario. Alternatively, the sentence could be written in the passive voice: “the script is derived from the alphabets.”

Compare these structures to choices C and D; do they say “is derived”? No, the GMATPrep sentence is not written in passive voice; rather, it uses the active voice: “derive/derives.” So the subject is actually “the northern and southern alphabets,” which is plural. The verb should be the plural “derive.” Eliminate D. The correct answer, by process of elimination, is C.

This last bit of analysis also shows the biggest trap in this problem: many students will think that the subject is “script” and that the verb should therefore be “derives.” Consequently, those students will eliminate the right answer, C, and choose a very tempting wrong answer, D. Another possible trap is exhibited in choice E, something we call false parallelism: students will like the apparent parallelism between “bringing with it” and “deriving from it,” but the two are only superficially parallel. There is no parallelism between the two pronouns and the second item doesn’t make sense in the context of the entire sentence.

The major take-aways here:

1. when doing SC, reuse your prior analysis as much as you can
2. scan SC answer choices vertically to find differences; don’t read horizontally
3. know how to recognize and properly construct noun modifiers and adverbial modifiers
4. watch out for parallelism markers – the markers are often little words but they can make a big difference!

* GMATPrep question courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.