Logical reasoning PrepTest 141 · Section 4 · Question 13

Incorrect. There could have been methane in the atmosphere before 2003 that scientists lacked the ability to detect, and that broke up because of exposure to UV radiation.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Methane falls apart when hit by sunlight, so any methane found in the Martian atmosphere must have been released recently.

Answer Anticipation:
The argument concludes that methane in the Martian atmosphere must have been released recently. Why? Because methane falls apart when hit by sunlight. That's relying on the assumption that the Martian atmosphere—and any gases in it—are regularly struck by sunlight. It's possible that sunlight doesn't hit certain parts of Mars, so the correct answer should highlight that gases in the Martian atmosphere are invariably hit by this light.

Answer Explanation:
This answer highlights the anticipated gap in the argument. If some methane in the atmosphere isn't ever exposed to sunlight, it could stick around, and the methane detected by scientists might therefore have been old.

Key Takeaway:
Don't get wrapped up in science! Stick to finding the gaps in arguments.

Incorrect. While the argument does rely on methane falling apart, it being detected before that process starts wouldn't kill the argument as long as it does, eventually, degrade.

Incorrect. The argument doesn't rely on this methane being exposed to UV radiation, but rather that any methane not recently formed had been so exposed and degraded. (And, of course, that the methane detected would soon be exposed to this radiation.)

Incorrect. Earth is out of scope of the argument. Additionally, this undermines a premise of the argument, so it can't be necessary for it.