In the 1960s,a lot of old city walls in Beijing________because people thought them useless.
__________ hours do you do your homework every day? Three hours every day.
_________Tom is not at home. He __________in the library.
Mr. Black is ___________to carry __________.
This man has _________ friends because he is not friendly.
Who taught them to ride bicycles? __________ They taught __________.