OG81 关于"，but“后加完整主谓结构的问题

浅浅123

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.

not caused by stress, alcohol, or rich foods, but

not caused by stress, alcohol, or rich foods, but are by

caused not by stress, alcohol, or rich foods, but by

caused not by stress, alcohol, and rich foods, but

caused not by stress, alcohol, and rich foods, but are by
印象中“，and”“，but"后面都要加完整的主谓结构，但在这题中却出现了例外，请NN指点~

浅浅123

答案为C

幸运E枪兵

not...but...结构需要对称的