3. A. ran

S2 + be + found + to have + PII
4. B. had finished

S + had + V3(ed/BQT) + O.
5. B. was watching

S + was/were + V-ing (+ O) 
6. B. has changed/have known

S+ has/ have+(not)+ Ved/ V3 ...

7. B. was having (câu `5`)

8. B. had left 

Before + S + V2/ed + O, S + had + V3/ed + O

9. C. had finished (câu `4.`)
10. D. arrived

S1 + V2 + as soon as + S2 + V2
11. B. will give

S + will + V
12. A. were preparing (câu `5`)

13. D. has lived (câu `6.`)
14. A. went 

Before + S + Ved / V2 , S + had + VpII
15. B. had opened (câu `6.`)

16. C. have tried (câu `6.`)
17. B. will have been

S + will have + PII 
18. A. looked/saw/had changed

S + V-ed, S2 + had P2
19. C. was living (câu `5.`)

20. B. wondered/hadn’t arrived/wrote (câu `6.`)

21. A. will have been working  (câu `17.`)
22. A. leave 

S + will be + P2 + (by O)
23. D. had written (câu `4.`)
24. A. was writing (câu `5`)
25. C. have tried  (câu `6.`)
26. B. left

S + V (d/ed) + since + mốc thời gian
27. B. had had

After + S + had + Vpp, S1 + V_ed/Vpp

Có vài câu mink sai có gì nhắc nhở ạ