11, Mr. Trung has been met many times.
12, Their homework hasn't been finished.
13, Have your friends been met by you yet?
14, The use of nouns in English is being studied by us.
15, The floor has been cleaned by them since 9:00 a.m
16, Football was played by them yesterday afternoon.
17, An accident was seen by me this morning.
18, Is chicken liked?
19, The party was enjoyed by us all.
20, The dictionary was bought by them last month.