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.www.ddhw.com Which one of the following is an assumption on which the argument depends?www.ddhw.com (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.www.ddhw.com (B) The fuel manufactured from the Martian atmosphere would not differ in composition from the fuel used to travel to Mars.www.ddhw.com (C) The device for manufacturing fuel from the Martian atmosphere would not take up any of the spaceship crew's living space.www.ddhw.com (D) A conventional spacecraft equipped with the device would not be appreciably more expensive to construct than current spacecraft typically are.www.ddhw.com (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.
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哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
雷达卡
发表于 2008-11-13 08:29:33
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千斤顶
发表于 2008-11-13 10:28:46
