求助一道prep上的题目。

43. 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

个人认为应该选C,因为这是一个not....but...的对称结构。答案给出的却是D,请高人指点一下；）