1)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.

2)当either… or… 与neither… nor，连接两个主语时，谓语动词与最邻近的主语保持一致。 如果句子是由here, there引导，而主语又不止一个时，谓语通常也和最邻近的主语一致。

Either you or she is to go.

Here is a pen, a few envelops and some paper for you.