Task 4:

1. the most horrible

2. most recent

3. the most boring

4. the most helpful

5. the most modern

6. the most expensive

7. the most difficult

8. most interesting

9. the most exciting

10. the most dangerous

Task 5:

1. have lived

2. has worked

3. has teached

4. didn't lived

5. put

6. is studying

7. watches

8. have been

9. didn't spend

10. saw

Task 6:

1. Where are they planting the trees?

2. When will she visit Hanoi?

3. Why does she have to stay in bed?

4. How often do you go to school?

5. What are Tom and Mai doing now?

Task 7:

1. If we plant more trees, the air will be fresher.

2. If we use recycled paper, we will save many trees.

3. If we cycle to school everyday, we'll keep fitter.

4. If we use recycled products, we will save money.

5. If people throw rubbish into the right bin, they will keep the environment cleaner.

Chúc bạn học tốt!