He ______ the key, so we ______ into the office.

Holiday shopping __________ be a tiring experience. There are so many places to visit and choices to make.

It has been announced that candidates ______ remain in their seats until all the papers have been collected.  

If you had joined the chat room ten minutes ago, you _____________what we were talking about.  

The boy         the first prize, but he was so careless as to make a foolish mistake.