You had better book rooms at the hotel in advance ________ you should find no room on your arrival.
7. No one but her parents _____ it.
6. The Olympic Games _____ held every _____ years.
5. About 40 _____ of the population of that country _____ on farms.
4. _____ can be done _____ been done.
3. He played on the _____ for two hours and when he returned he found half his goods _____ stolen.