there is 和 there are 的用法

there is a book , a ruler and 2 pens.

这里是就近原则。
后面紧跟的是a book所以用is
若紧跟的是2 pens用are

这是一个典型的倒装句----就是谓语动词（be）被放在了主语的前面。

There is a house nearby.
(there引导词，谓语is, 主语house，nearby地点副词)

还原成正语序：A house is there nearby.

使用is还是are，要看其后的主语是单数还是复数。单数is, 复数are.

就近原则
如
there is a book and two pens
there are two pens and a book

IS

就近原则，就是be动词最近的那个名词是单数或不可数名词的话就用is 复数用are

若原句改为there ( ) two pens ，a book and a ruler.
就用are

there is a book , a ruler and 2 pens.

单数和不可数名词用is
复数用are
这里是就近原则。
后面紧跟的是a book是单数所以用is
若紧跟的是2 pens用are

is

就近原则

there ( is ) a book, a ruler and two pens.

there ( are ) two pens, a ruler and a book.