вставьте предлоги (for,without,on,of about,before) в предложения:
What do we think________ when we use the words"The world around us"?
We see _______ us many things such as large lands and mountains,woods and rivers.
We know that there are many seas, lakes and rivers_____the Earth.
Water is a source_____ life on the earth. 
All living beings are not able to live_____ water.
Many rivers and lakes are polluted and cannot be used_____drinking.
Заранее спасибо!