Sam _____ some knowledge of the computer just by watching others working on it.
The first thing ____ you should do is to learn all the new words by heart.
The students are talking about the strange people and stories ____ they met in the adventure.
It is not I but Mr. Green who ____ in charge of the company.
____ much advice I gave him, he did exactly what he wanted to.
After living with his grandparents in the countryside for ten years, the boy returned to the big city ____ his parents worked.