33. A. did you do ⇒ were you doing
34. D. has already left ⇒ had already left
35. C. during ⇒ when
36. A. has disappeared ⇒ disappeared
dấu hiệu nhận biết: three days ago -> thì quá khứ đơn: S + V_ed
37. D. was cooking ⇒ cooked
38. C. saw ⇒ have ever seen
This is the first time + S + have/has + Vp2: Lần đầu làm gì.
39. B. graduates ⇒ had graduated
Khi hai hành động cùng xảy ra trong quá khứ, ta dùng thì quá khứ hoàn thành cho hành động xảy ra trước và quá khứ đơn cho hành động xảy ra sau.
40. B. had been ⇒ has been
41. D. They haven't visited me for five years.
42. A. Before Mike went to bed, he had turned off the light.
43. D. It is three months since I visited the muscum.
44. C. John has played the piano for 10 years.
45. A. I haven't seen her for a week.
46. A. It's a month since my father last smoked cigarettes.
47. C. Mr. Brown has had this car for five years.
48. A. It's years since I enjoyed myself so much.
49. B. We haven't been to the cinema for a long time.
50. D. I haven't seen Rose for three years.