UNIT 4 CHOOSE THE CORRECT WORD ( A , B , C OR D ) TO COMPLETE THE SENT...

21. Start at once or you will be late for school.(3)

A. If you start at once, you will be late for school.

B. Unless you start at once, you won’t be late for school.

C. You won’t be late for school if you don’t start at once.

D. If you don’t start at once, you will be late for school.