PrepTest 155

Incorrect. If anything, this answer supports the ruled-out explanation. (Though it wouldn't weaken the argument, as it doesn't overcome the reason the biologist ruled that theory out).

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
A tree in the Indian Ocean is descended from one from Hawaii. Since the seeds don't grow after being in sea water and the trees grow in the mountains, they couldn't have floated there. Seabirds carry seeds, so they probably carried them there.

Answer Anticipation:
This argument rules out one possible explanation (floating) in favor of another (seabirds). To strengthen this argument, the correct answer will either provide additional evidence against the ruled-out explanation, or evidence for the favored one. However, since the ruled-out explanation is fairly certainly ruled out ("the seeds will not germinate"), the correct answer is more likely to provide evidence that seabirds carried the seeds.

Answer Explanation:
This answer provides evidence in favor of the seabird theory. If there are species of birds that live in both places and nest in mountains, that increases the argument that seabirds carried the seeds from the mountains in Hawaii to the mountains on Reunion.

Key Takeaway:
When you're tasked with strengthening an argument that concludes an explanation for a phenomenon, the correct answer will generally provide evidence for the theory or evidence against a competing theory.

Incorrect. The argument establishes that AH is descended from AK, so AK's heredity is out of scope. Additionally, if anything, this would suggest an alternative location for the seeds to have come from, which wouldn't strengthen the seabird theory.

Incorrect. If anything, this answer supports the theory that the seeds floated from Hawaii to Reunion. Even then, the objection to that theory still stands.

Incorrect. If you selected this answer, you may have thought that it strengthens the argument by suggesting that the seabirds can fly for a long enough period to make the flight from Hawaii to Reunion. However, this answer doesn't specifically mention the seabirds that are common to Hawaii and Reunion, so it may be referring to completely different species.