In the nation of Partoria, large trucks currently have a much higher rate of traffic accidents per mile driven than other vehicles do . However, 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 the number of traffic accidents would be to require shippers to increase their use of triple-trailer trucks. Which of the following, if true, most seriously weakens the argument? . A Partorian trucking companies currently use triple-trailer trucks only for long trips using major highways , which is the safest kind of trip for large trucks. . B No matter what changes Partoria makes in the regulation of trucking, it will have to keep some smaller roads off-limits to all large trucks. . C Increased use of triple-trailer trucks would mean that large trucks would account for a smaller proportion of all miles driven on Partoria's roads than they currently do. . D In Partoria, the safety record of the trucking industry as a whole has improved slightly over the past ten years. . E The volume of truck traffic on Partoria's highways could be reduced by encouraging shippers to use rail transport whenever possible. A B C D E

The argument suggests that increasing the use of triple-trailer trucks would reduce traffic accidents because they have a lower accident rate compared to single and double-trailer trucks. To weaken this argument, we need to find an option that challenges the assumption that increasing the use of triple-trailer trucks would lead to fewer accidents.<br /><br />Option A states that Partorian trucking companies currently use triple-trailer trucks only for long trips using major highways, which is the safest kind of trip for large trucks. This option actually supports the argument by suggesting that triple-trailer trucks are already being used in the safest conditions.<br /><br />Option B mentions that no matter what changes Partoria makes in the regulation of trucking, it will have to keep some smaller roads off-limits to all large trucks. This option does not directly address the argument about the accident rate of triple-trailer trucks.<br /><br />Option C states that increased use of triple-trailer trucks would mean that large trucks would account for a smaller proportion of all miles driven on Partoria's roads than they currently do. This option weakens the argument by suggesting that the overall reduction in large trucks on the roads could lead to fewer accidents, not necessarily because of the type of truck, but because there would be fewer large trucks overall.<br /><br />Option D mentions that the safety record of the trucking industry as a whole has improved slightly over the past ten years. This option does not directly address the argument about the accident rate of triple-trailer trucks.<br /><br />Option E suggests that the volume of truck traffic on Partoria's highways could be reduced by encouraging shippers to use rail transport whenever possible. This option weakens the argument by proposing an alternative solution to reduce traffic accidents that does not involve changing the type of trucks used.<br /><br />Therefore, option C most seriously weakens the argument by suggesting that the reduction in the number of large trucks on the roads could lead to fewer accidents, not necessarily because of the type of truck, but because there would be fewer large trucks overall.