In which sentence are all pronouns used as objects of a preposition used correctly?
C. Tracey pushed the cart between I and Dad.
The object of a preposition can be a noun or pronoun. In sentence C, between would be the preposition, and I and Dad would be the object of the preposition. The remaining sentences are not examples of pronouns used as objects of preposition. Sentences A and B use the objective cases incorrectly, it should be: them instead of they, and her instead of she. Sentence C uses between you and me as subject and not as object of preposition.