Facebook is one of the most popular websites in Britain ___ over twenty-five million users.
I'm a singer is a program ______ is enjoyed by people of different ages.
A friend is a person who knows what you are saying ______ you are not talking.
It is true that knowledge ______ rather than being taught.
Don't give up, Tom. You haven't realized ______ great progress you've made!
Grace has been a teacher for two years. She ______ in a school when I first met her.