The use of radar detectors in commercial vehicles was banned because commercial truck and bus drivers were using these devices to drive faster than the posted speed limit without fear of arrest. Since drivers of noncommercial vehicles also use radar detectors and since speeding decreases safety for any vehicle, use of radar detectors should also be banned in noncommercial vehicles to increase safety. Which of the following, if true, most strongly supports the argument above? ['Traffic accidents involving a truck or bus generally pose a greater threat of injury or death than do other accidents.', 'Radar detectors are sometimes set off by devices other than the law enforcement devices that the radar detectors were built to detect.', 'In many places airplanes or helicopters are used rather than radar to locate vehicles traveling faster than the posted speed limit.', 'The ban on radar detectors in commercial vehicles has been effective in deterring them from speeding.']