题目选项分析

In the nation of Partoria, large trucks currently account for 6 percent of miles driven on Partoria's roads but are involved in 12 percent of all highway fatalities. The very largest trucks-those with three trailers-had less than a third of the accident rate of single-and double-trailer trucks. Clearly, therefore, one way for Partoria to reduce highway deaths would be to require shippers to increase their use of triple-trailer trucks. Which of the following, if true, most seriously weakens the argument?

【选项】In Partoria, the safety record of the trucking industry as a whole has improved slightly over the past ten years.