1. The scientific book has to be returned to the library by Phong

2. That old building must be repaired.

3. The memorial monument will be rebulit by the government.

4. Phong may be elected their leader by the students.

5.  Papers written in pencils won't be accepted by the teacher.

6. Some interesting places might be visited by the athletes after sea-games

7. Their house has to be cleaned up by Lan's parent before Tet holidays.

8. She might be interviewed by the principal.

9. Fruit must be kept in the fridge for long.

2.phong has to return the scientific book to thelibrary

=> The scientific book has to be returned to the library by Phong.

3.people must repairthat old building

=> That old building must be repaired.

4.the government will rebuild the memorial monument

=> The memorial monument will be rebulit by the government.

5.the students may elect phong their leader

=> Phong may be elected their leader by the students.

6.the teacher won't accept papers written in pencils

=> Papers written in pencils won't be accepted by the teacher.

7.the athletes might visit some interesting places after sea-games

=> Some interesting places might be visited by the athletes after sea-games.

8.lan's parents have to clean up their house before tet holidays

=> Their house has to be cleaned up by Lan's parent before Tet holidays.

9.the principal might interview her

=> She might be interviewed by the principal.

10.they must keep fruit in the fridge for long

=> Fruit must be kept in the fridge for long.