THE COMPUTER/ BREAK DOWN/ IF / YOU/ NOT KILL VIRUSES REGULARLY. A....

30. The computer/ break down/ if / you/ not kill viruses regularly.

A. The computer will break down if you don't kill viruses regularly.

B. The computer will break down unless you don't kill viruses regularly.

C. The computer won't break down if you don't kill viruses regularly.

D. The computer will break down unless you killed viruses regularly.