—I wonder why Susan looks worried today. —I’m not sure, but she _____a small accident driving here.

What way can you think of ______ the mice in the room?

－What does the sign over there say?－“No person _______ bring drinks into the student computer pool.”

Mr. Baker, a number of students want to see you. _______ they wait here or outside?

Mountain climbing ______ be really dangerous at times even though it is challenging and exciting in general.