Answer:
The children sailed paper boats before dinner.
Mothers call the children inside when dinner is ready.
She fell while she was playing and injured her knee.
Explanation:
Prepositional phrases are composed at least of a preposition and an object.
The word 'when' used as a conjunction means 'at the time that', and is followed by a subordinate clause.
The word 'while' is used to connect two events occurring at the same time, and is followed by a subordinate clause.
