You should understand the traffic rule by now. You’ve had it ________ often enough.
On snowy days, you have to drive very to avoid traffic accidents.
—You may find the key to the maths problem on page 107. —Ah, it’s so simple. I wonder why I _of that.
The long and tiring talk, filled with arguments and quarrels, ended in disorder, _________ no agreement at all.
Many people in the city wonder _____the city officials have the information they need to solve the problem.
So difficult _____ it to adjust to an English-speaking environment that he determined to learn English hard.