She looks very sad. I want to help her, but I just don’t know ____ to do it.
— I think students should have mobile phones to call their parents.—_____. They often use them to play games instead.
There's only one day to go. You _____ finish your schoolwork by tomorrow.
I want to relax myself right now. Would you please change to _____ music?
Lee is new in Nanchang. Maybe he needs a _____for sightseeing.
She always does very well in the English exams. But she can _____ understand English radio programs.