In early 2003, scientists detected

Answer choices

1. A

   Too Strong: nothing prior to 200313% picked this

   Mars had no methane in its atmosphere prior

   The author isn't thinking that methane suddenly burst on the scene in 2003. He just thinks that as methane leaks out of Mars, it gets zapped by UV radiation shortly thereafter, which dissolves it into its constituent bits.

   13%
2. B

   Correct58% picked this

   all methane in the Martian atmosphere is eventually exposed

   Why this is right

   This actually does resemble our Missing Link: if Martian atmosphere → constantly hit by UV If we negated this, would it Weaken? Sure! "Hey, author, some methane in the Martian atmosphere is never exposed to sunlight. So we might discover methane in the Martian atmosphere that's a million years old. If it was never exposed to sunlight, then we have no reason to think that something made it fall apart."

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

   58%
3. C

   Too Strong: cannot be detected12% picked this

   methane cannot be detected until it has started to

   The conclusion and evidence are not really about "detection" at all, so there's no reason for the author to assume anything about detection. This answer also sort of offends common sense, like "I couldn't taste the soup until you spilled it on the floor". It should be easier to detect intact methane then crumbling methane, right?

   12%
4. D

   Opposite16% picked this

   the methane that scientists had detected had been exposed to

   Had the methane the scientists detected been exposed to UV, it wouldn't have been methane; it would have just been loose hydrogen and carbon atoms (the building blocks of methane). The author thinks that once methane is exposed to UV, it falls apart (its hydrogen and carbon atoms falls apart into disconnected atoms). So the author is assuming that the methane the scientists detected had not been exposed to UV.

   16%
5. E

   Trap1% picked this

   methane in Earth's atmosphere does not fall apart as a result of exposure

   Opposite, if anything Out of Scope: Earth's atmosphere The author would believe that anywhere in the solar system that methane gets hit by the UV radiation in sunlight is a place where methane will fall apart. If we negated this and objected, "Not in Earth's atmosphere, it doesn't!", we wouldn't be weakening this conclusion, which is exclusively about the Martian atmosphere.

   1%