At weekends I prefer _______ at home to _______out.
I will never forget the day _____ we worked together in London.
________ your letter, I would have started off two days ago.
_______ you’ve got a chance, you might as well make full use of it.
He devoted himself ________ to his research work, having no time to play.
The girl looked at me with a ________expression at the ______ computer program.