Everyone knows that _____ is dangerous to play with fire, but _____ is difficult is to prevent children from playing with fire.
At present a special village _______ for the athletes from different countries to live in.
—Timmy, it is raining heavily out. Shall we stop here? —_______, we must finish this work today.
When his father came into his room, Tom pretended _______ a book.
Martin was sick with a strange fever; _______, he could neither eat nor sleep.
The company will be left in the _______ of the secretary when the manager is away.