21. I was met at her birthday ( by they )

22. that old tractor wasn't used to plough the hard soil

23. the food is cooked in the kitchen by Mrs.Green

24. Were English songs sung very beautifull by him ?

Cấu trúc :

* S + am/are/is + VpII + by + O 

* S + was/were + VpII + by + O

* Was/Were + S + VpII + (by O) ?

`21` `.` I was met at her birthday by they  .

`22` `.` That old tractor wwasn't used to plough the hard soil .

`23` `.` The food is cooked in the kitchen by Mrs . Green 

`24` `.` Were English songs sung very beautifull by him ?

Giải thích :

`-` Cấu trúc câu bị dộng thì QKĐ : S + was/were + P2 ( V3/ed )

`-` Câu trúc câu bị động thì HTĐ : S + am/is/are + P2 ( V3/ed )