When he was in that city, he _____ go to that park once a weeek.
—Can I join the club, Dad?—You can when you _____ a bit older.
If you are in any doubt as to _____ you should be doing these exercises, consult your doctor.
—When can I come for the photos? I need them tomorrow afternoon.—They_______ be ready by 12:00.
Was it _____ she heard with her ears ____ really made her frightened?
Beneath our feet _____ that our life depends on for food and clothing.