If everone in the city uses their own cars , the city will be seriously polluted by the smoke .
If everyone in the city uses their own cars , the city will be seriously polluted by the smoke . If everyone in the city uses their own cars , the city will be seriously polluted by the smoke . If everyone in the city uses their own cars , the city will become seriously polluted by the smoke . If everyone in the city uses their own cars , the city will be seriously polluted by the smoke .