1. were used
2. will be discussed
3. will discuss
4. was discussed
5. are built
6. be built
7. will be built
8. were built
9. are sold
10. sell
11. lock
12. is locked
13. was taken
14. will be taken
15. be taken
16. take
17. has taken
18. is taking
19. will meet, will take
20.met, took