请教prep sc1－74，谢谢

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

答案为D，但是这样不是破坏了not。。。but的平行了吗？请问 not...but是but后面省略了be吗？请牛牛解答，感激不尽。