11. You must write the answer on one side of the paper only.
--> The answer must be written on one side of the paper only.
12. We shall discuss the matter tomorrow.
--> the matter shall be discussed by us tomorrow.
13. The author will write the book in june.
-->the book will be written by the author in june.
14. Someone has already paid the electrician for his work.
--> the electrician has been already paid for his work.
15. We use your book in our class.
-->Your book is used in our class by us.
16. Someone has broken one of my dinner plates.
-->one of my dinner plates has been broken .
17. You must plan your work carefully.
-->Your work must be planned carefully.
18. They are sending Mr. Brown abroad on business.
-->Mr Brown are being sent abroad on business.
19. You should open the wine about four hours before you use it.
-> the wine should be openned about four hours before you use it.
20. You mustn't switch on a light.
-->A light mustn't be switched on.