About one fourth of the families in the city have private cars and this number _____ to double in five years.
There were signs here and there, _____ people to look out for ___rocks.
From his ___ voice, I have to say that you are really ____.
—Why did the girl spend the whole day __ up in her room, ____? —She failed in the college entrance examination.
When ___ this medicine, it is a good idea to avoid ______ alcohol.
My father ___ my brother for driving but he wanted to pick ___ the knowledge of the computer during his spare time.