11. The lesson is explained by the teacher.
12. The food is being cooked in the kitchen by Mrs Green.
13. That noise was made by these boys.
14. English is spoken all over the world.
17 The bill has to be paid by them before the first of the month.
18. You will be asked several questions.
19 The box has been locked and can't be opened by me.
20 You are wanted to do this work by me now.