Sorry, I am late. I _____ have turned off the alarm clock and gone back to sleep again.
We _____ on this project for four hours. Let’s have a rest.
Experiments of the kind ____ in both the U.S. and Europe well before the Second World Wall.
By the time Jane gets home, her aunt ____ for London to attend a meeting.
His sister left home in 1998, and ______ since.
The water ____ cool when I jumped into the pool for morning exercise.