平行语法下并列句是否需要介词,及实义动词是否可省略

betowin

Recently physicians have determined that stomach ulcers are not caused by stress, alcohol, or rich foods, but a bacterium that dwells in the mucous lining of the stomach.

　　(A) not caused by stress, alcohol, or rich foods, but

　　(B) not caused by stress, alcohol, or rich foods, but are by

　　(C) caused not by stress, alcohol, or rich foods, but by

　　(D) caused not by stress, alcohol, and rich foods, but

　　(E) caused not by stress, alcohol, and rich foods, but are by

本题中答案C,且是大家都认为很简单的一个题目，但是我有两个疑惑，第一个：就是平行下为什么不是stress, alcohol,  rich foods, 与bacterium的平行，且这四个原因都在by的引导下，那就不用but后面加by了。

第二个：我印象中应该是白勇语法下里有提到，并列句的之实义动词不能随便省略，但本题答案C的实义动词caused被省略了，这是不是说明在并列句中即使是实义动词也是可以省略的

二零一八

说一下个人看法  c选项中stress,alcohol,rich foods本来就是和bacterium平行的
如果是but are caused by ，就是和 are not caused by stress,alcohol,rich foods平行
如果是but caused by， 就是和 not caused by stress,alcohol,rich foods
如果是 but by 就是和 by stress, alcohol, or rich foods..
不知道对不对