A preposition is a word which shows how the verb acts on the subject of a sentence.
The dog jumps over the gate.
Here the gate is the object, jump is the verb and over is the preposition.
The cat sits on the chair.
Here the chair is the object, sits is the verb and on is the preposition.
Here are twelve prepositions:
across after around between near on through to towards under up with
Read this story and choose the right preposition. Use each preposition once. Then look at the answer page.