Hi,

To make the question simple, I generalize the sentence structure as follow:

Many teenagers undergo stress, - CLAUSE 1

but results {of a recent study} indicate that the patterns of stress that girls experience are more likely to result in depression than are those that boys experience. - CLAUSE 2

But in the CLAUSE 2, we even have another clause in it:

CLAUSE 2 - but results {of a recent study} indicate [Clause 2.1] that the patterns of stress that girls experience are more likely to result in depression than are those that boys experience.

In this clause 2.1 there is a comparison/ parallel structure:

the patterns of stress that girls experience VS. the patterns of stress that boys experience

For that we can eliminate:

B, "What" replaces for "stress" not "the patterns of stress". Boys experience stress, not the patterns of stress.

C & D, "would" and "do" do not parallel with "are" in Clause 2.1

E: lacks the verb "experience", thus changes meaning.