EX1:
11. C 12. D 13. C 14. C 15. C
EX2:
1.B 6.C
2.A 7.C
3.A 8.A
4.B 9.A
5.C 10.B
EX3:
1. Letters are typed by Mary in the office.
2. You will be helped by his father tomorrow.
3. Human life has completely been changed by science and technology.
4. This bottle was broken by Peter.
5. English is being learnt in the room.
6. My mind can be changed.
7. I hadn't been told about it.
8. Her telephone number isn't known by me .
9. The children will be brought home by my students.
10. A present was sent to me last week.
