1. Cows aren't kept over there.

2. Is most of the farm work done by machine?

3. Our exercise at home is corrected by the teacher.

4. His mother was worried by Ali's absence.

5. Several new schools in our town are being built.

6. Great progress in industry, science and medicine has been made.

7. A lion was killed by Sam last week.

8. Your report must be handed in before the end of this month.

9. Researches on global warming began to be carried out by scientists two years ago.

10. A great deal of tea in England is drunk.

1. They don't keep cows over there.

⇒ Cows aren't kept over there.

2. Does machine do most of the farm work?

⇒ Are most of the farm work done by machine ?

3. The teacher corrects our exercise at home.

⇒ Our exercise at home is corrected by the teacher.

4. Ali's absence worried his mother.

⇒ Ali's mother was worried by his absence

5. They are building several new schools in our town

⇒ Several new schools are being built in our town.

6. We have made great progress in industry, science and medicine.

⇒ Great progress has been made in industry, science and medicine.

7. Sam killed a lion last week.

⇒ A lion was killed by Sam last week.

8. You must hand in your report before the end of this month.

⇒ Your report had to hand before the end of this month.

9. Scientists began to carry out researches on global warming two years ago.

⇒ Global warming was beginning to carry out researches by scientists two years ago.

10. People drink a great deal of tea in England.

⇒ A great deal of tea is drunk in England.