ANSWER 4: The practices of PREPOSITION

These are the answers for the exercise of preposition.

1. on 
2. in 
3. at 
4. with 
5. on
6. among
7. for
8. in
9. of 
10. after
11. by
12. from
13. across, towards
14. At
15. Since 

Don't forget that you can always review the lessons at http://grammar520.blogspot.com/2015/06/the-introduction-of-preposition.html.