in 在……里
on 在……上面( 与物体接触)
under 在……下面
there is / are 有( 某地有某物) ,就近原则,即最靠近它的名词是单数或不可数名词时用is ,否则用are
如
They are in the room .
There is little milk in the bottle .
There is a book on the table .
There are two books on the table
There is a dog under the table .
祝你假期愉快!加油!不明白再问!