—Mary, could you tell me if your mother ________ our school sports meeting tomorrow?　　—I think she will come to school if she _________ free.　　

Few people knew how to use the Internet in the past,_____?

I think he is a student, ____？

---He seldom revised for exams, ___________ he? ---___________. He always got low marks in exams.

The traffic accident _____ last Sunday morning.