When we have a sentence as long and confusingly ordered as this one, a really good move is to eliminate anything unnecessary to the grammatical structure of the sentence. This can help us to figure out what exactly the sentence is actually saying and pinpoint errors in sentence construction. Some good candidates for elimination are parts of the sentence set off by commas and long descriptive phrases - we should be able to remove anything that provides "extra" information and still have a grammatical sentence. For example,

• This Thursday afternoon, I went to the potluck at Julianne and Michelle's apartment.

can be simplified to

• I went to the potluck.

without messing up the grammar.

Let's do the same thing with our sentence:

• Young Athenian women collaborated to weave a new woolen robe and that this robe depicted scenes of a battle.

Much simpler! Now we see that the sentence is divided into a series of two parts ("Young ... woolen robe" and "that ... battle") separated by a conjunction ("and"). We also see that the last portion of the sentence is not underlined. Whenever we see that we have a series where part of the series is underlined and part is not, we should immediately start looking for parallelism issues.

Looking at our two parts, we see one big difference in grammatical structure:

• Young Athenian women collaborated to weave a new woolen robe

• that this robe depicted scenes of a battle

Since the part of our series that isn't underlined begins with "that", we need the other part to include "that" to match. Looking through the answer options, only D uses the word "that" twice, giving us correct parallel structure.

We actually featured this problem recently on the PrepScholar GMAT blog as one of the 5 Hardest Sentence Correction Questions. I recommend checking out the article for more strategies and trends we can take away from this and other 700+ level problems!