`2.` sets

`-` Sự thật hiển nhiên `->` Thì hiện tại đơn

`4.` doesn't rain

`7.` returns

`-` DHNB: somtimes `->` Thì hiện tại đơn

`8.` is writing

`-` DHNB`:` at present `->` Thì hiện tại tiếp diễn

`12.` taught

`-` DHNB`:` ago `->` Thì quá khứ đơn

`-` teach - taught - taught: dạy

`13.` fell/ got

`-` fall - fell - fallen: ngã

`-` get - got - got/ gotten

`14.` was sitting

`-` DHNB`:` When `->` Thì quá khứ tiếp diễn

`15.` will visit

`-` DHNB`:` next week `->` Thì tương lai đơn

`16.` was reading

`-` DHNB: while `->` Thì quá khứ tiếp diễn

`17.` haven't spoken

`-` DHNB: since `->` Thì hiện tại hoàn thành

`-` speak - spoke - spoken: nói

`18.` have tried/ haven't succeeded

`-` DHNB: for, yet `->` Thì hiện tại hoàn thành

__________________________________________________

`-` Thì hiện tại đơn:

$(+)$ S + V(s/es)

$(-)$ S + don't/ doesn't + V

$(?)$ Do/Does + S + V?

`-` Thì quá khứ đơn:

$(+)$ S + Ved/V2

$(-)$ S + didn't + V

$(?)$ Did +  S + V?

`-` Thì quá khứ tiếp diễn:

$(+)$ S + was/were + V-ing

$(-)$ S + was/were + not + V-ing

$(?)$ Was/Were + S + Ving?

`-` Thì hiện tại tiếp diễn:

$(+)$ S + am/is/are + V-ing

$(-)$ S + am/is/are + not + V-ing

$(?)$ Am/Is/Are + S + V-ing?

`-` Thì hiện tại hoàn thành:

$(+)$ S + have/has + V(pp)

$(-)$ S + have/has + not + V(pp)

$(?)$ Have/Has + S + V(pp)?

`-` Thì tương lai đơn:

$(+)$ S + will + V

2. The sun (set) sets in the West

4. It (not rain) doesn't rain  in the dry season.

7. The doctor sometimes (return) returns home late.

8. He (write) is writing  a long novel at present.

12. His uncle (teach) taught English in our school five years ago.

13. The old man (fall) fell as he (get) got info the bus.

14. When I saw him, he (sit) was sitting asleep in a chair.

15. She (visit) will visit her aunt next week.

16. Last Monday, while I (read) was reading book, the phone rang.

17. They (not speak) haven't spoken to each other since they quarreled.

18. I (try) have tried to learn English for years, but I (not succeed) haven't succeeded  yet.