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`@` Cấu trúc thì QKĐ -> HTHT:

`a,` The last time + S + Ved/V2 + O + was + time

`=` S + last + Ved/V2 + O + time

`=` It's + time + since + S + (last) + Ved/V2 + O

`=>` S + has/have + not + Vpp + O + for/since + time 

`b,` When + S + did + V-inf + O

`=` How long + have + S + Vpp + O?

`=` How long ago + did + S + V-inf + O?

`=` How long is it since + S + Ved/V2 + O?

`c,` S + started/began + to V/V-ing + when/in/on/at time...

`->` S + has/have + Vpp + O + for/since + time

`d,` This/It is the first time + S + has/have + Vpp + O

`->` S + has/have + not + Vpp + O + before

`->` S + has/have + never + Vpp + O + before

`1,` It's 3 months since Tom last had his hair cut.

`2,` The last time my father went to Hanoi was 2 years ago.

`3,` It is years since I last enjoyed myself so much.

`4,` I last ate this kind of food 2 years ago.

`5,` How long have they driven a car to work?

`6,` How long have he flied the kite?

`7,` How long have you studied English?

`8,` How long have you done research on lung cancer?

`9,` He hasn't gone abroad before.

`10,` She has driven for ten months.

`11,` We have eaten since it started to rain.

`12,` I last had my hair cut when I left her.

`13,` The last time she missed me was 5 months ago.

`14,` It is a long time since we last met him.

`15,` The last time I saw him was eight days ago.

`16,` It is Monday since I last took a bath.