`(5)`

`1.` I haven't seen Minh for a fornight.

`2.` It's two years since Tom (last) visited his uncle.

`3.` It's three years since we (last) went to My Son.

`4.` When did he buy the computer?

`->` Form: When did + S + V?

`=` How long + have/has + S + V3/ed?

`5.` It's the first time I have talked to the headmaster.

`->` Form: It's is the first time + S + have/has + V3/ed

`=` S + have/has + never + V3/ed + before

`6.` The last time we were in London was many years ago.

`7.` We haven't eaten this kind of food since January.

`8.` We have lived here for fifteen years.

`9.` It's five months since she (last) visited me.

`10.` We last met uncle Tam three years ago.

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* Form (câu `1 ->4; 6->10`):

S + have/has + not + Vpp + for/since + time

`=` It is + time + since + S (last) + V2/ed

`=` S + last + V2/ed + time + ago

`=` The last time + S + V2/ed + was + time + ago