If ____unsolved, the problem of food safety may lead to more serious results.
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.