IV.
1. do -> did
2. teach -> taught
3. send -> sent
4. spend -> spent
5. begin -> began
6. cut -> cut
7. put -> put
8. give -> gave
9. write -> wrote
10. be -> was / were
11. buy -> bought
12. have-> had
13. take -> took
14. go -> went
15. make -> made
16. think -> thought
17. see -> saw
18. eat -> ate
19. sing -> sang
20. wear -> wore
XII.
1. Brush your teeth after meals
2. Don't play soccer in the street
3. Wash and iron your own colthes
4. Don't eat too much candy
5. Wash your hands before meals
6. Don't worry about the examination
7. Tidy your room every day
8. Don't forget to write to your parents