`1.` They built this school 30 years ago.

`2.` They are going to announce the results of the contest.

`3.` The doctor examined the patients.

`4.` The librarian arranges the books into sections.

`5.` Ann has made some tea for her.

`6.` We hadn't found anything before the police arrived.

`7.` People said that Nam was a clever pupil.

`8.` Has Tom finished the work?

`9.` How did the police find the lost man?

`10.` They may use this room for the classroom.

`11.` They will introduce this speed limit gradually.

`12.` She will wear evening dress.

`13.` They will have to find someone to take her place.

`14.` New Arts Gallery will exhibit my paintings for the first time.

`15.` You could put your money to good use instead of being left idle in the bank.

`16.` They are lenghtening the runways of all the main airport.

`17.` You must keep this door shut.

`=>` Câu chủ động:

`-` Thì QKĐ:

`+` Với động từ thường:

`(+)` S + V2/ed 

`(?)` Wh-word + did + S + V(bare)? 

`+` Với động từ tobe: `(+)` S + was/were + N/Adj 

`-` Thì TLG: `(+)` S + is/am/are + going to + V(bare)

`-` Thì HTĐ: `(+)` S + V(s/es)

`-` Thì HTHT:

`(+)` S + have/has + V3/ed

`(?)` Have/Has + S + V3/ed? 

`-` Thì QKHT: `(-)` S + hadn't + V3/ed

`-` Với động từ khuyết thiếu:

`+` May: `(+)` S + may + V(bare) 

`+` Have to: `(+)` S + have/has to + V(bare)

`+` Could: `(+)` S + could + V(bare)

`+` Must: `(+)` S + must + V(bare) 

`-` Thì TLĐ: `(+)` S + will + V(bare)

`-` Thì HTTD: `(+)` S + is/am/are + V-ing