Mong các a chị giúp em với ạ cảm ơn nhìu ạ

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: 

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

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

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

Structure 3: 

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

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

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15. C

16. B

17. B

18. A

19. A

20. A

`color{orange}{~MiaMB~}`