Recently physicians have determined that stomach ulcers are not caused by stressl 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
题目分析：不就是一个not 和but引导的并列关系嘛，not后面用by所以but后面为了保持对应应该也加by，符合这个要求的只有C。今天生活真美好，遇到这么个傻了吧唧的题！
