A year ago the government reduced the highway speed limit, and in the year since, there have been significantly fewer highway fatalities than there were in the previous year. Ttherefore, speed limit reduction can reduce traffic fatalities. The argument is most vulnerable to the criticism that it takes for granted that ['highway traffic has not increased over the past year', 'the number of traffic fatalities the year before the new speed limit was introduced was not abnormally high', 'the new speed limit was more strictly enforced than the old', 'the majority of drivers obeyed the new speed limit']