The Peaks of a mountain range, acting like rocks in a streambed,produce ripples in the air flowing over them;the resulting flow with crests and troughs that remain stationary although the air that forms them is moving rapidly,arepattern, known as "standing waves".

A. crests and troughs that remain stationary although the air that forms them is moving rapidly,are
B. crests and troughs that remain stationary although they are formed by rapidly moving air ,are
C. crests and troughs that remain stationary although the air that forms them is moving rapidly,is
D. stationary crests and troughs although the air that forms them is moving rapidly,are
E. stationary crests and troughs although they are formed by rapidly moving air ,is

friends its a OG-11 SC question , i want to understand why the option (E) is "awkward and unclear".Thanks in advance.

I actually think C is correct; I was only attempting to explain why E wasn't the best choice.

The resulting flow is the subject after the comma. Thus, eliminate everything except for C and E.

E is out because they do not refer to the air and distorts the original meaning of the sentence.

Thus, I think it's C, too.

I also think the answer is C. It's a problem of subject-verb agreement, and flow being singular, the verb should be "is" and not "are". That's why only C and E are taking in consideration.

I pick C.

Same logic as the above.

What's the OA?

C for me.

option (E) is worng for few reasons:

stationary crests and troughs although they are formed by rapidly moving air is

(1) 'stationary' applies to crests only which is incorrect
(2) the sentence is supposed to show contrast with the help of 'although'...something like this...."crests and troughs are [stationary] although the air that forms them is [rapidly moving]....option (E) is not showing this contrast and is changing the meaning.

This is simple. Flow is singular so the answer should have is. Down to C and E. E changes the meaning. So C it is.
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I will not go beyond saying that C is more wholesome than E. I would not say. E is awkward or E lacks contrast. As long as the three elements are there namely, stationary on one side, rapidly moving on the other side and the contrast –marker 'although' in between, then I feel the contrast is established. The only faint reason why C was weighed in might have been because ‘the crests and troughs that remain’ is parallelly matched by ‘the air that forms’

How can we dispute an OG OA!
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IMO: Why will it not refer to both crests and troughs? If I say, ‘this class comprises intelligent boys and girls, will it mean only boys? How else are we going to use compound objects?
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” I truly believe in online learning, I have been a student in both an Ivy League school (brick and mortar) and in an online setting and I have learned 1,000 times more in an online setting. You do not have anyone there lecturing you and then you do the work, online you are made to do it all yourself. Amazing how different the results are. - Heather(a student)”

Alicia Helle, an online student at the UW, "Obtaining my degree online has been a blessing. With two small children, I am able to work when it is convenient for my family and me. I have nothing but positive comments and experiences from my time at UW-Stout.”

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Agree that C is the correct answer. But besides introducing a passive, which in itself is nowhere a sin except in GMAT, you cannot fault E.
E does not omit the restrictive relative clause "crests and troughs that remain stationary" because it states the similar "stationary crests and troughs".

To reuse your example in the same way that E is formulated:
Yellow bananas are tastiest although brown ones are good for baking. Neither awkward, nor unclear.

E also weakens the contrast made necessary by "although". C states that "....remain stationary although the air .... moves rapidly". E makes this contrast less obvious, but nonetheless present.

So I don't see this one as clear cut as it might seem from the posts.