The Irish playwright John Synge wanted to see Ireland free both of Eng

• SHORT ANSWER
I explain "once outside, twice inside" in the longer analysis below.

The word "both" is the parallelism marker in the correlative conjunction Both X and Y.
The X element and the Y element must be parallel, and whatever is attached to the X element does not "carry over" to the Y element.

1) Eliminate B because the X and Y elements are not parallel. In option B
X = of England (preposition + noun)
Y = [her own] parochialism (noun)
→ We have an impermissible "once inside" situation.
→ The word of is "inside" the structure Both X and Y only once. The word of must be "twice inside."

2) Eliminate options D and E for using "as well" unnecessarily.
→ the words both/and already signal that Ireland needed to be rid of England and Ireland's own parochialism.
→ the words as well are redundant.


3) Compare option A to option C.
Option C is better; it uses "of" before both objects, whereas the use of "from" and "of" in option A makes it seem as though the phrases mean different things.
On rare occasions, the phrases have slightly different meanings.
This question is not one such occasion.
GMAC will never test you on that issue.

But GMAC will test your ability to choose the better option.
When parallelism is at issue and you have one option that produces identical X and Y elements, choose that option.
We should stay with the repeated free of in option C rather than create confusion

The best answer is C

• PARALLELISM, MARKERS, AND ONCE OUTSIDE, TWICE INSIDE

The most common marker of parallelism is the word "and."
When we have X and Y, if there is a preposition before the X element, that preposition will often carry over to the Y element.
→ Correct: He went hiking with Anton and Benjamin.
→ The "with" before "Benjamin" carries over or is implied, this way: He went hiking with Anton and [with] Benjamin.

If the preposition comes after the parallelism marker "both," correlative conjunctions such as Both X and Y do not function in the same way as X and Y.
→ Correct but not standard [preposition should be repeated]: He went hiking both with Anton [preposition + noun] and with Benjamin [preposition + noun].
Watch the placement of the preposition with.
→ Correct and standard: He went hiking with both Anton [noun] and Benjamin [noun].
→ Wrong, once inside: He went hiking both with Anton [preposition + noun] and Benjamin [noun].

Unlike a "regular" parallel marker such as "and," in Both X and Y, whatever is attached to X does not carry over to Y once the correlative conjunction "kicks in."
We must repeat ourselves.
The word "both" marks the beginning of the parallel structure.
Imagine brackets acting as a fence around [both X and Y].

If the preposition comes before the marker word both, then the preposition is outside the construction and we use that preposition only "once outside."
If the preposition comes after the marker word both and therefore precedes the X element, we repeat the preposition before the Y element—"twice inside."

The X and Y objects may require different prepositions.
[X and Y, Correct:] I sprayed cleaning fluid on the counter and under the table.
BOTH X and Y, Correct: I sprayed cleaning fluid both on the counter and under the table.
In both examples, X and Y are parallel.

But if the X and Y elements do not require different prepositions, no reason exists to use different prepositions.
I'll mark off the "outside" of the construction with vertical blue lines.
→ X and Y, Correct: She traveled by airplane and passenger train.

→ Both X and Y, Correct: She traveled by || both airplane and passenger train. || ["by" is "once outside"]
→ Both X and Y, Correct: She traveled || both by airplane and by passenger train.|| ["by" is "twice inside"]
→ Both X and Y, Correct but weird: She traveled || both by airplane and via passenger train. ||
→ Both X and Y, Wrong: She traveled by || both airplane and via passenger train. || ["once outside, once inside"]

ELIMINATE B
We eliminate option B because it use the preposition "of" once inside, a placement that is incorrect.
Wrong: . . . free || both of England and her own parochialism || (once inside)

Eliminate D and E
We eliminate options D and E because as well is redundant and GMAC doesn't like the phrase much.

Option C is better than option A
True, in both options, a preposition is "twice inside."
But why, as in option A, are we using different prepositions, of and from?
Is there any good reason to do so?
I can't think of one.

By contrast, we have option C: the preposition of is the same and is properly repeated.
Hence the word of is properly "twice inside" the structure.
Option C is better than option A.

The best answer is C.

• NOTES

This issue of preposition (or verb) placement in correlative conjunctions is tested fairly often on the GMAT.

I have posted a few questions that test correlative conjunctions and parallelism.

I recommend that you try this question, here, and read my explanation in this post, here.

That question and its explanation are good ways to cement this "once outside, twice inside" hack into your mind.

COMMENTS

eakabuah , Enkhhulan , and zhanbo , you are all spot on.

Very nicely done.

Kudos to all.