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题库 / OG2017-CR-619
Transportation expenses accounted for a large portion of the total dollar amount spent on trips for pleasure by residents of the United States in 1997, and about half of the total dollar amount spent on transportation was for airfare. However, the large majority of United States residents who took trips for pleasure in 1997 did not travel by airplane but used other means of transportation.
If the statements above are true, which of the following must also be true about United States residents who took trips for pleasure in 1997?
Most of those who traveled by airplane did so because the airfare to their destination was lower than the cost of other available means of transportation.
Most of those who traveled by airplane did so because other means of transportation to their destination were unavailable.
Per mile traveled, those who traveled by airplane tended to spend more on transportation to their destination than did those who used other means of transportation.
Overall, people who did not travel by airplane had lower average transportation expenses than people who did.
Those who traveled by airplane spent about as much, on average, on other means of transportation as they did on airfare.
情景：交通花费占据旅行总花费的很大比重，并且有一本的交通花费是花给了航空公司。但是，很大一部分旅游的人并没有通过飞机来旅行，而是用了其它的交通方式。
推理：通过本题的问题可知，它是演绎推理。
选题方式：略
选项分析：
A选项：大部分用飞机飞行的人这么做的原因是飞机的成本最低。
B选项：大部分用飞机飞行的人这么做的原因是其它的交通方式无法抵达他们的目的地。
C选项：平均每一英里的花费上，那些坐飞机的人比用其它交通方式的人花费了更多。本选项有些迷惑性。我们从推理文段中无法得知几种交通方式行进的英里数，因此，平均每一英里的花费就更加没法计算了。
D选项：Correct. 总的来说，不坐飞机旅行的人们比那些坐飞机旅行的人们有更低的平均花费。
E选项：那些坐飞机旅行的人们在航空方面的花费平均和他们用其它交通方式的花费相同。
我的确被c迷惑了，以至于眼瞎没看到d选项
In option C, per mile cost is not a proper factor because the miles traveled in any mode of transportation is not given.
eg if the total miles traveled in air were significantly less than those traveled in other modes, then Avg cost of air (= tot miles * cost per mile) would be comparatively less and the total dollar amount for air would decrease and the argument won't hold true.”
费用A占总体一半，A使用者少于一半，则A使用者人均费用超过总体人均费用或其他群体人均费用。这就是个DS题。
“机票/总费用=50%，坐飞机的人/总人数
“机票/总费用=50%，坐飞机的人/总人数
我是这样想的。假设全部transportation花费100元，一共10人，2人坐飞机花了50，剩下的8人别的交通方式花了50，那飞机人均费用大于其他交通工具的人均费用。
对啦
因果写反了。因是大部分美国人乘坐飞机
老师。可以理解为是果因推理吗。相当于是A however notB 。果是:大部分美国人都是乘坐飞机 因是花在飞机上的费用占总交通费的一半 找一个他因削弱推理。 选D，给出了一个他因，由于飞机更贵，其他交通方式更便宜
CD都是一个均值啊？没有办法得出乘飞机的总花费占交通总开销的大头啊？为什么D可以C不行呢？
其实这本质上是一个数学题。 发给是坐飞机和不坐飞机对半开的。但是坐飞机的人却比不坐飞机的人少，所以是以人数来取平均值的，即是D选项。而C选项是在人均上又取了一个每英里的平均数，因为英里数未知，所以是推不出来每英里选择不同交通方式的人的花费的多少的。我最开始也选了C， 后来琢么了一下，应该是D才对。
楼上说的挺好。
谢谢解释！我明白啦！
文段说总体不坐飞机的人花费少+总体不坐飞机的人多，所以不坐飞机的人均花费一定是低的！
❀۹(*´ᗜ`*) 给你花花！
我明白啦！
❀۹(*´ᗜ`*) 也给老师花花！
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答案错了，是D