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PART A/
I/
1. C /s/ còn lại /d/
2. D /ɪə/ còn lại /eə/
II/
3. danger
4. protect
5. such
6. place
7. solve
III/
8. B get rid of
9. C Polluted
10. D : sự biến mất
11. B ought to : nên
12. B passed 
13. A part
14. B destruction

15. D can be held

PART B/
I/
16. into
17. at
18. against
19. off
20. for
II/
21. had taken
22. was having
23. met
24. has been built
25. won't go
26. serviced
27. drinks
28. got
29. had asked
30. are playing

III/
31. Unless he wears his coat, he'll be cold.
32. If you don't keep silent, you won't understand the lesson.
33. If I hadn't spent too much time on games, I could have finished the task.
34. If my sister hadn't stayed up so late last night, she wouldn't feel tired now.
35. If the weather weren't bad, we will go on a trip.
36. How many languages are spoken in Switzerland?
37. Gold was discovered in California in 1848.
38. You should not go swimming in cold weather.
39. The job can't be done by the workers.
40. The floor hasn't been cleaned by Jean yet.