We'll supply you with the products only __________ you prove your ability of payment.
—Look at the timetable. Hurry up! Flight 4062 __________ off at 18:20. —I will.
It__________ long before we __________the result of the experiment.
If you __________ attend the party , you'd better leave now.
I don't know whether my sister will come or not, but if she __________ , __________.
Food supplies in the flood-stricken area __________. We must act immediately before there's none left.