Você sabe usar adequadamente as preposições  in, on, at? Elas podem ser usadas para designar tempo ou lugar.

Abaixo seguem algumas dicas para estudo e aprendizado do uso de IN, ON, AT.

PREPOSTION OF PLACE

In

Use ‘in’ with spaces that you can physically walk into, or place something into:

in a room / in a building

in a garden / in a park

Use ‘in’ with bodies of water:

in the water

in the sea

in a river

Use ‘in’ with lines:

in a row / in a line

in a queue

At

Use ‘at’ with places in a town, city or other community:

at the bus-stop

at the door

at the cinema

at the end of the street

Use ‘at’ with places on a page:

at the top of the page

at the bottom of the page

Use ‘at’ in groups of people:

at the back of the class

at the front of the class

On

Use ‘on’ with vertical or horizontal surfaces that you can lay something onto, or attach something to:

on the ceiling / on the wall / on the floor

on the table

Use ‘on’ with small islands:

I stayed on Maui.

Use ‘on’ with directions:

on the left

on the right

straight on

IMPORTANT NOTES

In / at / on the corner

We say ‘in the corner of a room’, but ‘at the corner (or ‘on the corner’) of a street’

In / at / on the front

We say ‘in the front / in the back’ of a car

We say ‘at the front / at the back’ of buildings / groups of people

We say ‘on the front / on the back’ of a piece of paper

PREPOSTION OF TIME

In

Use ‘in’ with months, years and periods of time such as decades or centuries:
in January
in 1978
in the twenties
Use ‘in’ a period of time in the future to express that an action will occur after that amount of time:
in a few weeks
in a couple of days

At
Use ‘at’ with an exact time:
at six o’clock
at 10.30
at two p.m.

On
Use ‘on’ with days of the week:
on Monday
on Fridays
Use ‘on’ with specific calendar days:
on Christmas day
on October 22nd

Se quiser testar seu aprendizado, faça o teste online. A correção é automática e você já fica sabendo quanto tirou. Depois me diz qual foi a sua nota.

http://esl.about.com/library/quiz/blgrquiz_prep1.htm