IN / AT / ON (Position)

In
Study these examples:
The fish is in the water and the fisherman too.
- in the sea
- in a river
- in the swimming pool

Tom is in a line
- in a queue
- in a row

Ann is in a class
- in a building
- in a town
- in a country


At
Study these examples:
Who is that man standing at the door?
- at the window
- at the bus-stop

- at the top (of the page)
- at the bottom (of the page)

- at the end of the street
- at the back
- at the front



On
Study these examples:
- An apple is on the book
- O’clock is on the wall

- on the table
- on the floor