Please excuse me _______ your letter by mistake.
Although you have learned much knowledge and a lot of theories, the problem is _______ can be put into practice.
If you have the chance to take charge of the department, the first thing to do is to find out what _______ of you.
It is one thing to enjoy listening to good music, but it is _______ another to play it well yourself.
To be admitted to a key university, _______.
The job is not very profitable ________ cash, but I can get valuable experience from it.