74.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.
(C) because they enhance reproduction or survival, but
(D) because they enhance reproduction or survival, but are
想询问实战上C、D的解题方法/观念
看了Ron及语法笔记的解释仍然不太明白为何选C会造成ambiguous
感谢各位版上神人释疑！！

but后面要S+V,but(many biological traits)are

(C)but会有两种解释方式,一种是你提的,另一则是跟because后面的子句做转折,如果读者还要花时间去思考那句子就不够concise,补出are可以让读者直接对到第一种