If we do ______, soon giant pandas will die out.
-_______ do you have an English party?-Once a month.
We never celebrate Christmas, _______ they do it every year.
What's wrong with my son's_______? He can't see things clearly.
-How long does it_______ you to ride a bike to school?-About 20 minutes.
Students in our school have a class meeting_______3 p.m_______ every Tuesday.