.I had been puzzled over the problem for over an hour without any result, _____ all at once thesolution flashed across my mind.
As a student, you should try to ______ being late for your class.
This is ______ difficult problem that few students can work it out.
A notice was ________ in order to remind the students of the changed lecture time.
This is not a match. We’re playing chess just for ______.
They made the longest sofa in the world. It is ten times ______ the ordinary ones.