Satellite navigation systems (satnavs) for cars, in which computer voices announce directions as you drive, save fuel and promote safety. Studies show that, when assigned to novel destinations, drivers using satnavs took, on average, 7 percent fewer miles per journey than drivers using paper maps. Fewer miles driven means, on average, less fuel consumed. Also, the drivers who used satnavs drove more carefully in that they were not taking their eyes off the road to check paper maps. Which one of the following, if true, most strengthens the argument? ['Drivers who are given directions as needed are less likely to change course suddenly or make other risky maneuvers.', 'Drivers who do not routinely need to drive to an unfamiliar location are more likely to plan out their route carefully prior to departure.', 'The more fuel a vehicle consumes, the more motivation a driver has to find the shortest route to his or her destination.', 'Drivers who own satnavs usually prefer to drive to their accustomed destinations by using their customary routes rather than by following the directions given by the satnavs.']