« on: September 13, 2005, 03:01:26 AM »
The conclusion is that the components of plutoís atmosphere are N, CM, and M in order of decreasing abundance right. In order for this argument to stand, Answer choice C is required as an assumption.
Negate C: If there was some other frozen substance on the surface of Pluto that vaorizes more readily than M but less readily than CM, the conclusion for that ordering of N -> CM -> M would not be correct.
Letís call that some other frozen substance B. if the assumption is false, the order would be N -> CM -> B -> M, which is not the conclusion stated in the stumulus.
The answer would be equally credible if the assumption said there is no other frozen substance on the surface of Pluto that vaporizes more readily than CM but less readily than N. Itís a defender assumption, which is kinda hard to prephrase before you read the answer choices.