用there be 结构（有）
如：There is a book on the desk.桌上有一本书.
a book是主语
on the desk是状语
There是引导词（单独没什么意义
is随主语变化
There are some books on the desk.桌上有好几本书.
用there be 结构（有）
如：There is a book on the desk.桌上有一本书.
a book是主语
on the desk是状语
There是引导词（单独没什么意义
is随主语变化
There are some books on the desk.桌上有好几本书.