费费逻辑宝典12，求解答

lena_go

12. The only physical factor preventing a human journey to Mars has been weight. Carrying enough fuel to propel a conventional spacecraft to Mars and back would make even the lightest craft too heavy to be launched from Earth. A device has recently been invented, however, that allows an otherwise conventional spacecraft to refill the craft’s fuel tanks with fuel manufactured from the Martian atmosphere for the return trip. Therefore, it is possible for people to go to Mars in a spacecraft that carries this device and then return.

Which one of the following is an assumption on which the argument depends?

(A) The amount of fuel needed for a spacecraft to return from Mars is the same as the amount of fuel needed to travel from Earth to Mars.

(B) The fuel manufactured from the Martian atmosphere would not differ in composition from the fuel used to travel to Mars.

(C) The device for manufacturing fuel from the Martian atmosphere would not take up any of the spaceship crew’s living space.

(D) A conventional spacecraft equipped with the device would not be appreciably more expensive to construct than current spacecraft typically are.

(E) The device for manufacturing fuel for the return to Earth weighs less than the tanks of fuel that a conventional spacecraft would otherwise need to carry from Earth for the return trip.

此题正确答案是e，为什么b c d 不对呢，还有e的逻辑关系我迷糊啊

LuckiPanda

这题我刚做过，顺手答了
题目说在火星上可以制造出燃料，所以提供了不带回程燃料的可能性（防止超重无法带）

B不对，管它燃料是什么成分，能做燃料就行了，不是必要的假设
C不对，和是否占用乘员的生活空间没关系，是说重量
D不对，和造价也没关系，题目没提到任何预算啊造价啊之类
E对的，要是这个制造新燃料的设备本身比回程燃料都要重，那还要考虑这种可能性干什么？直接带回程燃料不就好了。所以是必要假设，至少这设备要比回程燃料轻，才值得考虑这种可能性。

lena_go

thanks,boy

lena_go

我还有疑惑，请问楼上的牛牛，，我知道这道题感觉上的正确答案是最后一个，而且其他为无关，例如 b，可是如果新产生的燃料如果和出发的时候不一样，那飞船不能function 阿，推广到c d就是这样的选向属于假设马，为什么不行

luweihaororo

以下是引用lena_go在2007-7-13 15:17:00的发言：

我还有疑惑，请问楼上的牛牛，，我知道这道题感觉上的正确答案是最后一个，而且其他为无关，例如 b，可是如果新产生的燃料如果和出发的时候不一样，那飞船不能function 阿，推广到c d就是这样的选向属于假设马，为什么不行

路过，不好意思越俎代庖一下：）

“如果新产生的燃料如果和出发的时候不一样，那飞船不能function 阿”这是lz用常识推的，原文没说。C、D同理，原文只关心燃料是不是太重，所以宇航员生存空间、造价之类都没关系。

顺便说一下，我们诉诸于常识，B也不对。举个简单例子，有些汽车的发动机，能烧汽油也能烧柴油；所以，燃料composition不一样，飞船未必就不能烧。

lena_go

是的楼上的牛牛提醒了我原文没说，只就是无关，颇有体会，谢谢谢谢。送你一个