请教GWD-28-Q17

Q17:

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?

1. Partorian trucking companies have so far used triple-trailer trucks on lightly traveled sections of major highways only.
2. 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.
3. Very few fatal collisions involving trucks in Partoria are collisions between two trucks.
4. In Partoria, the safety record of the trucking industry as a whole has improved slightly over the past ten years.
5. In Partoria, the maximum legal payload of a triple-trailer truck is less than three times the maximum legal payload of the largest of the single-trailer trucks.

 正确答案是A, 想不明白为什么B错, 请各位NN帮忙看一下,谢谢!!!