51 I haven't gone swimming since we were in Spain

52 It's weeks since you tidied this room

53 We have started to look for a flat for five months.

54 I haven't been to a night club before 

55 this is the first time They have heard such a thing

56 This is the first time his authority has been challenged.

57 It is two years since she left university

58  I have never known a more warm-hearted person than my mother.

59 It is over a year since I last saw them

60 It has started to rain for 2 hours

Cấu trúc thì Hiện tại hoàn thành :
S + have/has + PII 

51. I haven't gone swimming when we were in Spain.

52. It's weeks since you tidied this room.

53. We have looked for a flat fot 2 months and we are still looking.

54. I haven't been to a night club before.

55. This is the first time they have heard such a thing.

56. This is the first time someone has challenged his authority.

57. It's 2 years since she left university.

58. I have never known a more warm-hearted person than my mother.

59. It is over a year since I last saw them.

60. It has started to rain for 2 hours.

* Cấu trúc: S + haven't/hasn't + Vpp + for/since + time. 

              = S + last + Ved ... time + ago

              = The last time S +Ved + was + time + ago

              = It is + time + since + S + last + Ved

Chúc em học tốt. Xin 5 sao và CTLHN.