Section 2 STRUCTURE, page 268

Find mainverb
Answer :
6. of, in
7. have
8. have , are
9. are, iis
10. was
11. is, will be
12. must
13. at, as
14. is
15. who
16. would be
17. is
18. its
19. are known
20. are
21. is
22. is
23. is
24. is
25. may

Section 2 STRUCTURE, page 291

6. present perfect tense
7. present perfect tense
8. present tense
9. simple past tense
10. simple present tense
11. simple present tense
12. simple past tense
13. simple present tense
14. past progressive tense
15. simple present tense, future tense
16. past progressive tense, simple past tense
17. simple present tense
18. present tense
19. simple past tense
20. simple present tense
21. present tense
22. simple past tense
23. simple present tense
24. simple past tense
25. present tense