以下是引用weiyu在2004-3-26 21:01:00的发言: -- 作者:Energy -- 发布时间:2003-12-21 22:22:00
-- 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.
我选B; E不对,因为说less有问题,是加油后的总重量,不是单独的tank重量. 但是如果两种能源的组成不同,就能说明问题了.
还是认为E对。weiyu,你的前半句话我没看明白。但是后半句话有问题。文章第一句话就说“The only physical factor preventing a human journey to Mars has been weight. ”所以组成的问题在这里是out of scope. |