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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32. John hasn't had his hair cut for over six months. 

33. When did you last ride a bicycle? 

34. When did he last write to you? 

35. How long is it since he talked to you? 

36. How long is it since you telephoned him?

37. It's the first time we have eaten this kind of food. 

38. I have never seen this film before. 

39. He hasn't gone abroad before. 

40. She has driven for 1 month. 

41. We have eaten since it started to rain.