GMAT Sentence Correction (SC) | Re: Floating in the waters of the equatorial Pacific, an array

Hi guys,

1.In A, "interaction that affect..." is modifier as explained, but I saw it as a run on sentence as first, so i ruled it out. Is it a modifier because of the meaning and why can't I see it as a run on sentence?
2.In B, can someone please give me more detail why it is wrong? because "awkwark" is not enough for me to understand. Is it because "with" modify "atmosphere" so it is wrong modifier?

Thanks in advance!

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