prep12一道事故死亡率的题，纠结

神粥八宝

Prep2012-Pack1-CR-012 VCR005853 Easy

The faster a car is traveling, the less time the driver hasto avoid a potential accident, and if a car does crash, higher speeds increasethe risk of a fatality. Between 1995 and 2000, average highway speeds increasedsignificantly in the United States, yet, over that time, there was a drop inthe number of car-crash fatalities per highway mile driven by cars.

Which of the following, if true about the United Statesbetween 1995 and 2000, most helps to explain why the fatality rate decreased inspite of the increase in average highway speeds?

A. The average number of passengers per car on highwaysincreased.

B. There were increases in both the proportion of people whowore seat belts and the proportion of cars that were equipped with airbags assafety devices.

C. The increase in average highway speeds occurred as legalspeed limits were raised on one highway after another.

D. The average mileage driven on highways per car increased.

E. In most locations on the highways, the density ofvehicles on the highway did not decrease, although individual vehicles, onaverage, made their trips more quickly.
我选的是D，答案是B，我知道B是有道理的，但是不知道为什么D不对，有可能是我理解问题。我的逻辑是这样的：每公里事故数=总事故数/总行驶公里数，B是减少了总事故数，D是增加了总行驶公里，两个不都行吗。。。求解答。谢谢！！

Reasoning

What could explain why the number of fatalities per highwaymile driven declined even as average highway speeds increased? We are told thathigher speeds mean a higher risk of fatalities, other things being equal.Consequently, the increasing highway speeds between 1995 and 2000 should haveled to more fatalities per highway mile driven.

Since the fatalities per mile driven actually decreased,some countervailing factor must have increased driving safety more than enoughto compensate for the danger of the higher speeds. Thus, find an answer optionsuggesting how a factor that increased driving safety became more common oreffective between 1995 and 2000.

A. More passengers per car would likely mean even morefatalities per highway mile driven, since more people would die per caraccident.

B. Correct. More seatbelts and airbags would haveprobably reduced the average number of fatalities per car accident, resultingin fewer fatalities per mile driven even if the higher speeds resulted in morecar accidents.

C. This cannot help explain the decrease in fatalities.Driving at a higher speed probably increases the risk of a fatal car accidentregardless of whether the speed is legal or illegal.

D. Fewer accidents per highway mile driven could explain whythe average highway mileage per car increased (since some cars would have gonemore miles before crashing), but the converse is not correct: the increased averagemileage could not explain why there were fewer accidents per mile driven.

E. Instead of explaining why there was a decrease in thenumber of fatalities per highway mile driven, this merely rules out thepossibility that the explanation was a lower density of cars on the highways.

The correct answer is B.

上面是我粘贴的几年前cd上的，讨论没看懂两道Prep2012的CR，第10，12题，求解答~~

https://forum.chasedream.com/forum.php?mod=viewthread&tid=863358&fromuid=1278748

(出处: https://forum.chasedream.com/)

我把帖子放到这里
还是想问一下是不是死亡率跟事故率不太一样  反正就是不明白啊
求大神
谢谢！！！！！！！！！！！