1. study
2. is
3. have just taken
4. haven't received
5. arrive
6. studied
7. have to
8. still don't decide
9. have never had
10. had
11. enjoyed
12. think
ответ:1) study
2)are
3)have just taken (just, указывает на perfect)
4)haven't received ( yet, указывает на perfect)
5)arrived
6)studied
7)have to
8) still haven't decided (still, указывает на perfect)
9)never had
10)had
11)enjoyed
12)think
Объяснение: