The ones bolded I believe are prepositions (Well what I would have chosen):
3. After this ball, you may run to first base.
4. Did Jill leave her suitcase outside the door?
5. You may sit behind me or on the floor.
6. A picture of our great grandmother was placed above the fireplace.
7. Are you throwing the ball onto the roof or over the house?
8. At noon, the parade will move past the courthouse.
9. She had hurried across the busy street among a large crowd.
10. He has practiced for two hours since the last game.
11. By five o’clock, the saleslady will have driven sixty miles.
12. Within an hour of the party, they had cleaned.
13. A bear might have come down that trail recently.
14. I shall sit in the middle of the first row.
15. Everyone except the bus driver had gone into the restaurant.
