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题库 / Prep2012-CR-12
The faster a car is traveling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars.
Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?
The average number of passengers per car on highways increased.
There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.
The increase in average highway speeds occurred as legal speed limits were raised on one highway after another.
The average mileage driven on highways per car increased.
In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.
For why D is wrong, it may be explained as: there is a certain number of fatalities per highway mile driven say 0.01. It doesn't matter how many miles were driven exactly. This only implies that if 100 miles were driven, there was one fatality. If 1000 miles were driven, there were 10 fatalities. If 10000 miles were driven, there were 100 fatalities. The fact that people have started driving more does not increase/reduce this number. (credit to gmatclub forum)
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