Prep一题中not but用法 求助

ChinaHawk

Prep SC中有一题是：Paleontologist SJ(人名) 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 radom by-products of other evolutionary development.
答案是：because they enhance reproduction or survival, but are

这里not 和but 要求平行的结构 那么答案的 Be not... but be 的结构算是平行么？比较困惑。
谢谢

suners

回复 1# ChinaHawk

麻烦楼主把问题和答案贴全，方便自己也方便他人。

Vickyliu

not but结构当中not在动词后面时是绝对平行的
比如 Lilei was killed not by Hanmeimei but by Jim
但是not位于助动词后时并列谓语
比如 Lilei was not killed by Hanmeimei but was killed by Jim

题中就是第二种情况~~

ChinaHawk

thanks

sylivayjer

谢谢三楼 我也学习到了