—Whose English book is this?
—It _______ be Lily’s, but I’m not sure.
might
can’t
must
In the street I met the professor_______gave us a talk last week.
-Would your brother go for a picnic this Sunday7 -If I don't go,____.
You must______your cigarette when you are at the gas station.
Her grandparents are still in good health_____they are over eighty.
-What do you think of his concert? -Oh,no one does____.