prep-43 怎么也想不明白

答案D not...but...为什么不平行,C为什么不对?请帮忙翻译

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

这题是有难度。个人觉得平行是相对的，不是绝对的（虽然这题我也做错过）。PREP解释的很好，MM仔细体会体会？

(C) but可能作为介词,产生because they enhance reproduction or survival, but simply random by-products的歧意