–Has your father returned from American yet ? --Yes, but he ____here for only 3 days before his company sent him to Australia.
The window is never opened ____ in summer.
Nobody knows it ____ me.
I don' t think Xiao Li is ____ the other students ____ mathematics.
_____ hearing the news, I was wild ____ joy.
My father began to work ____ a bus driver when he was twenty years old.