After her son’s death, the old lady __________ sit at the window, deep in thought.

It is very important that you _______ for this examination.

Without the air to hold some of the sun’s heat,the earth at night　　　.

--- How did you like the concert last night? --- I enjoyed it very much, but the dancers ______ a better job.

He insisted that the book _______ to the school library at once.