让人晕乎的一道prep题呀！NN快来

SJG 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      

这里的random是由副词simply修饰的形容词，

所以不可能是they random,

而必须加上Be动词，they are random.

CD语法上都没错

C：not but

D：主语（are not 。。。），but [省略主语]（are 。。。）

D比C更好些，只是D better 一些

－－－－－－－－－－－－－－－－－－－

这题类似的题讨论过了

http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=184669&page=2

谢谢亲爱的版主！ 赞成上述说法！再次证明了GMAT的题，相对错误不容忽视！