The reason ______ she gave for being absent was _____ the heavy snow prevented her coming.
— Shall we go out for a walk? — Oh, ________.
— My son spoiled your carpet. Let me buy you a new one. — ________.
Natural disasters occur at ________ times, so it is always difficult to warn people in advance.
________ when your ticket has been checked will you be allowed to take the plane.
Sometimes we can see more than 60 students are ________ in a small school bus, which can easily cause traffic accidents.