`4,` John has learned French since `2021`

`5,` I haven't gone to the cinema for ages

`6,` I haven't eaten octopus before

`7,` It has rained here for a fornight

`8,` When did you start to live here ?

`9,` The last time they went out with each other was two years ago

`10,` Bill is the most intelligent student I have ever met

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     `**` Chuyển QKĐ `->` HTHT

`@` S + last + V2/ed + ... + t/gian + ago

`->` The last time + S + V2/ed + ... + was + t/gian + ago

`->` It's + time + since + S + last + V2/ed ...

`->` S + have/has + not + P2 + ... + for + t/gian

`@` This is the first time + S + have/has + P2 ...

`->` S + have/has + not + P2 + ... + before

`->` S + have/has + never+ P2 + ... + before

`@` S + started/began + to V/V-ing + ... + t/gian + ago

`->` S + have/has + P2 + ... + for + t/gian

`@` How long + have/has + S + P2 ... ?

`->` When + did + S + start/begin + to V/V-ing ... ?

Các công thức đổi HTHT - QKĐ

Structure 1: 

S + has/have + not + V3/ed + for/since + time 

--> S + last + V2/ed 

--> The last time + S+ V2/ed + was + time 

--> It is / has been + time + since + S+ (last) + V2/ed 

Structure 2: 

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

--> When + did + S + V1?

--> How long is it + since + S+ V2/ed ?

Structure 3:

S + has/have + V3/ed + for/since + time 

--> S + started / began + to V / Ving 

--> It is / has been + time + since + S+ V2/ed 

Structure 4: 

S + has/have + not/never + V3/ed + ... before

--> This/It is the first time + S+ has/have+ V3/ed

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4. John has learnt French since 2021.

5. I haven't gone to the circus for ages.

6. I have never eaten octopus before.

7. It hasn't rained here for a fortnight.

8. When did you move here? / When did you start to live here?

9. The last time they went out with each other was two years ago.

10. Bill is the most intelligent I have ever met.

`color{orange}{~MiaMB~}`