In

At

On

零介系詞

(the) bed*
the bedroom
the car
(the) class*
the library*
school*

class*
home
the library*
the office
school*
work

the bed*
the ceiling
the floor
the horse
the plane
the train

downstairs
downtown
inside
outside
upstairs
uptown

* 對這些位置，你有時可以使用不同的介系詞。