Spectroscopic analysis has revealed

Answer choices

1. A

   Out of Scope: surface amounts25% picked this

   There is no more frozen nitrogen on the surface of Pluto than there is either frozen

   The author hasn't committed to any comparisons about the amounts of each element or molecule on the surface of Pluto. And if we negated this and said, "There is more frozen nitrogen ice than there is ice of the other two" that would only seem to strengthen the author's conclusion that nitrogen is the most prevalent.

   25%
2. B

   Too Strong1% picked this

   Until space probes reach Pluto, direct analysis of the atmosphere

   Too Strong: impossible Out of Scope: space probes This argument is only about the prevalence of difference gases in Pluto's atmosphere. It has nothing to do with whether we can or can't directly analyze the atmosphere. We can still reach solid conclusions about things even with indirect evidence. The author doesn't need to assume we need direct analysis, and she doesn't need to assume that space probes (which were not even mentioned) are necessary for that end.

   1%
3. C

   Correct52% picked this

   There is no frozen substance on the surface of Pluto that vaporizes more readily than methane but less

   Why this is right

   This looks somewhat appealing, because we were anticipating an assumption about how readily nitrogen vs. CO2 vs. methane vaporize. It's a little unappealing for not mentioning nitrogen, but this is Necessary Assumption, not Sufficient. The answer doesn't have to prove the conclusion. If we negate this answer, would it weaken? Yes. If we said, "Hey, author, there is a frozen substance on Pluto that vaporizes more readily than methane but less readily than CO2", then the author's conclusion would be wrong in saying that methane is ranked #3 in terms of prevalence. This mystery substance would be our new #3, if it vaporizes more readily than methane but less readily than CO2. Since negating this answer weakens the argument, it's a correct answer. When Necessary Assumption answers are ruling out an idea with a word like "no" or "not", take the time to negate it. These answers often will not sound like any sort of idea we've predicted. We're usually only going to see their impact / relevance if we negate them (and they're the easiest type of claim to negate, because we just remove the negative word).

   Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

   52%
4. D

   Too Strong: only if18% picked this

   Nitrogen is found in the atmosphere of a planet only if nitrogen ice is found on the

   The author didn't need to assume that for every single planet in the universe, if we find nitrogen in the atmosphere, we find nitrogen ice on the surface. Just because that's true on Pluto doesn't mean the author is assuming it's true for all planets.

   18%
5. E

   Out of Scope3% picked this

   A mixture of nitrogen, carbon monoxide, and methane is characteristic of the substances from which

   Out of Scope: how Solar System formed This argument isn't positing any claims about the relationship of Pluto's top 3 atmospheric gases to the component substances that formed the Solar System.

   3%