--_______may I keep this book? --For two weeks.
Mr. Black comes from England, and he has stayed in China for three years. So you can talk with him ________.
It is difficult for us to learn a lesson in life _______ we've actually had that lesson.
One fifth of the work _______ by computer last year.
This is the very thing ______ belongs _____.
She kept on _______ until midnight though he was tired.