We may find that learning a foreign language does not have to be________learning our mother tongue,but can in fact be twice ________.
Please keep me _____ what happens.
______ the chairman of the council, the vice chairman does duty for him.
In the competition to be held, a gold medal, together with a certain sum of money, _____ the champion.
You can only be sure of _____ you have at present; you cannot be sure of something _____ you might get in the future.
The traditional view is _____ we sleep because our brain is “programmed” to make us do so.