13. The desk must ______ (clean) once a day.

12. The stone bridge______________ (build) in our hometown for ten years.

11. When I got to the station, the train ____ already ______ (leave).

10. I didn't know what __________ (happen) to China in a century.

9. She said that the car___________ (use) the next week.

8. ----When ______ you______ (see) him?　

----I______ (see) him last Sunday.

7. You _______ (come) here last year, ______ you?

6. How long ______you_______ (live) in this town?

5. It's better to give than__________ (receive).

4. The Whites____________ (not listen) to the radio at that time.