Passive voice 11-21, можна не все делать

11. My friends have been invited to tea
12. An English book has been given to me.
13. Has the letter been written yet?
14. A lot of interesting things have been told to us.
15. The paper have been written without mistakes.
16. The matter was discussed some days ago.
17. You are wanted on the phone.
18. My book was found on the windowsill.
19. Excellent shelters have been built in these mountains.
20. The exercises have been given out to all the students.
21. The boy was angry because he wasn’t allowed to go to the stadium by his mother.