*Giải thích:
- The last time + S + Ved/V2 + O + was + time (trong QK)
-> S + has/have + not + Vpp + O + for/since + time (trong QK)
- It's + time (trong QK) + since + S + (last) + Ved/V2 + O
-> S + has/have + not + Vpp + for/since + time (trong QK)
- S + started/began + to tướng V/V-ing + O + time (trong QK)
-> S + has/have + Vpp + for/since + time (trong QK)
- This is the first time + S + has/have + Vpp + O
-> S + has/have + not + Vpp + ... + before
-> S + has/have + never + Vpp + ... + before
* Answer :
`51` I haven't gone swimming since we were in Spain
`52` It's weeks since you (last) tidied this room
`53` We have looked for a flat for 2 months and we are still looking
`54` I haven't been to tướng 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 not been challenged (Câu tiêu cực thì Hiện Tại Hoàn Thành : S + has/have + been + Vpp + by O)
`57` It is 2 years since she (last) left university
`58` I have never known a more warm-hearted person than thở my mother
`59` It is over a year since I last saw them
`60` It has rained since 2 o'clock