请帮忙看一下PREP 1-74

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

答案是D

偶选了C，觉得题目很明显在考trailts are not the products ----, but simply random by-products

觉得D中but are 的are多余，偶错在哪里？请指教

詳請請參見prep語法筆記,在這簡單說明如下:

在文法裡,有幾個字需要特別留意,如before,after,since,but等等,因為這些字可以當作連接詞、

介係詞甚至副詞等多種詞性，以本例而言，如果不加are,會讓人誤以為but可以當介係詞,如此

與not....but的用法不同，當然本題純就字面意思是很難察覺這點，需要瞭解詞性及句子結構