The traffic management bureau required drivers to use headlights during the day as well as at night when they passed a certain road section, and found that the annual accident rate on this road was 15% lower than before. They concluded that the citywide Enforcing this requirement will similarly reduce accident rates. The one that best supports the above argument is:. ['The test road section was selected to include a variety of road conditions that may be encountered when driving in the city.', 'The traffic volume of the tested section was reduced during the test because other routes can be selected.', 'Under certain conditions, including fog and rain, most drivers already use headlights during the day.', "Drivers' understanding of the requirements for using headlights on this test section comes from three prominent signs in each direction of travel."]