prep 74的疑问

74. (28503-!-item-!-188;#058&003635)

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

答案选D。 我选的是C。

答案说：(C) but可能作为介词,产生because they enhance reproduction or survival, but simply random by-products的歧意
(D) 正确，but are表明了but在这里只能作为连词,构成be not… but (be)…的平行结构

我觉得not the products of natural selection。。。不是正好和but  simply random by-products of other evolutionary developments对称吗？

你看到的平行沒錯啊，就是要用are來確定這個平行  明確比較對象也很重要

沒有的話 結構上也可以解釋為跟because那段平行   就造成歧意了   所以有比沒有好

平常的規則是說not...but之後的be可以省   但是省略可能造成歧意  就是不省比較好

一點淺見

我觉得是不是因为后面其实省略了they（traits ） 所以其实but后面是but (they) are...这样？？