feifei 12

carolzxy1 · 发表于 2011-11-27 22:46:44

12. The onlyphysical factor preventing a human journey to Mars has been weight. Carryingenough fuel to propel a conventional spacecraft to Mars and back would makeeven the lightest craft too heavy to be launched from Earth. A device hasrecently been invented, however, that allows an otherwise conventionalspacecraft to refill the craft’s fuel tanks with fuel manufactured from theMartian atmosphere for the return trip. Therefore, it is possible for people togo to Mars in a spacecraft that carries this device and then return.

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

A. The amount of fuel needed for aspacecraft to return from Mars is the same as the amount of fuel needed totravel from Earth to Mars.
B. The fuel manufactured from theMartian atmosphere would not differ in composition from the fuel used to travelto Mars.
C. The device for manufacturingfuel from the Martian atmosphere would not take up any of the spaceship crew’sliving space.
D. A conventional spacecraftequipped with the device would not be appreciably more expensive to constructthan current spacecraft typically are.
E. The device for manufacturingfuel for the return to Earth weighs less than the tanks of fuel that aconventional spacecraft would otherwise need to carry from Earth for the returntrip.

選的b為什麼選e呢？求高人指教，順便能說一下怎麼做assumption麼？做了n多assumption都錯。。。。。求思路

sdcar2010 · 发表于 2011-11-27 23:09:19

Necessary assumption. Use negation.

If you negate E, you have:
The device for manufacturing fuel for the return to Earth DOES NOT weigh less than the tanks of fuel that a conventional spacecraft would otherwise need to carry from Earth for the return trip.

If this is the case, what is the point of carrying the heavy device to Mars??? A dead weight??? Thus, the argument falls apart. E) is necessary for the conclusion to be drawn.

feifei 12

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