4. came - had been

5. had finished - went

6. left - had studied

7. had cleaned - moved

8.  applied - had investigated

9. came

10. had printed - came

12. left - had had

13. had graduated - became

14. came - had eaten

15. was

16. was eating - entered

17. had prepared

18. was bought

19. was

4.came /had been .

-> By the time + S +Ved/cột 2 , S+had +Vpp 

5. had finished/went 

-> After + S+had +Vpp , S+Ved/cột 2 

6. left/had studied 

-> Before +  S+Ved/cột 2 , S+had+Vpp 

7. had cleaned/moved 

->  S+had+Vpp +before + S +Ved/cột 2 

8.applied /had  investigated 

->S +Ved/cột 2 + after + S +had +Vpp 

9. came 

-> thì QKĐ ,dấu hiệu :last month 

-> S + Ved/cột  2

10. had printed / came 

-> S + had +Vpp + by the time + S + Ved/cột 2 

12. left/ had had 

-> Before + S + Ved/cột 2 , S + had +Vpp 

13. had graduated / became

-> After + S + had +Vpp , S+ Ved/cột 2 

14. came/was eating 

-> When + QKĐ +QKTD 

15.was

-> thì QKĐ,dấu hiệu : ago 

16. ate/ was entering 

-> While +QKĐ , QKTD 

17. was preparing 

-> Thì QKTD 

-> S + was/were +V-ing

18. was bought 

->Câu bị động ở thì QKĐ : S + was/were +Vpp + By +O 

19. was

-> thì QKĐ ,dấu hiệu : last month 

@Chaeyoung