No one can deny that it is ______ that many more residents could have been injured if the building had fallen at midnight.

have you been —I got caught in traffic, otherwise I_______ here earlier.

What do you think of the game called “trick or treat”—_______________.

The boy, with his classmates, often ______ to the library on weekends.

In those days bikes were not ______ used because few people could afford (负担起) to buy one.