Các công thức đổi HTHT - QKĐ

Loại 1: 

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

--> S + last + V2/ed 

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

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

Loại 2: 

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

--> When + did + S + V1?

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

--> How long ago + did + S + start / begin + to V / Ving? 

Loại 3:

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

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

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

Loại 4: 

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

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

Loại 5:

When + did + S + last + V1?

--> When + was the last time + S + V2/ed? 

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Ví dụ loại 1:

I haven't seen him for 4 days.

- The last time I saw him was 4 days ago. 

Ví dụ loại 2:

How long have you learnt English? 

- When did you learn English? 

Ví dụ loại 3:

My father has smoked for five years.

- My father started smoking five years ago. 

Ví dụ loại 4:

I have never eaten this kind of food before.

- This is the first time I have eaten this kind of food. 

Ví dụ loại 5: 

When did you last telephone him?

- When was the last time you phoned him?