英语一些词汇的be动词是跟前还是跟后的

我想你想问的是主谓一致这一语法现象中的就近原则.
当there be 句型的主语是一系列事物时,谓语应与最邻近的主语保持一致.
　　There is a pen,a knife and several books on the desk..
　　There are twenty boy-students and twenty-three girl-students in the class.
　　总的来说,在由not only…but also…,not just…but…,or,either…or…,neither…nor…连接主语的句子中及在there be句型中,谓语动词的单复数按就近原则处理,即按与谓语动词最靠近的那个主语来确定谓语动词的单复数形式.如：
　　Not only John but also I am going to Shanghai next week.
　　Either you or she is to go.
　　There is a pen,a few envelops and some paper for you.

就近原则，与邻近主语保持一致

He is not only my favorite teacher but also my good friend.
I will either go shopping or watching a movie at this weekend.
I am neither a doctor nor a nurse.
一般来说动词在连词之前。