SC: Paleontologist Stephen Jay Gould

[FeiH991]

Paleontologist Stephen Jay Gould has argued that many biological traits are not the products of natural selection, favored due to their enhancement of reproduction or survival, but that they are simply random by-products of other evolutionary developments.

(A) due to their enhancement of reproduction or survival, but that they are

(B) due to the reproduction or survival they enhance, but they are

(C) because they enhance reproduction or survival, but

(D) because they enhance reproduction or survival, but are

(E) because of enhancing reproduction or survival, but are

OA: D
Dear instructor, I understood that choice C might has ambiguity problem since there is a modifier between the commas. But I still have the problem about Not ... but ... II ism. Is D paralleled? Don't understand why " are not " can parallel with "but are" should it be" not are" and "but are"?
Thank you in advance.

[RonPurewal]

that is actually answered here:
https://www.manhattanprep.com/gmat/foru ... ml#p123958

i understand why you didn't find that thread (this isn't the head question of the thread—i'm realizing that only now, too late). check it out.