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#72672
Complete Question Explanation

Strengthen, CE. The correct answer choice is (B).

This causal argument attacks one causal explanation and identifies an alternate causal explanation in its conclusion. The argument attempts to explain what could've caused a tree species on one island (Reunion Island) to be descended from a tree species on a different island (Hawaii). The argument attacks those who suggest the seeds of the Hawaiian species drifted over the ocean to Reunion Island, because seeds soaked in seawater will not germinate. The argument also notes that the trees are found in the mountains, not near the shore, undermining the idea that drifting on the ocean could've transferred Hawaiian seeds to a mountain region on Reunion.

The argument concludes instead that seabirds caused the transfer of Hawaiian seeds to Reunion Island, because seabirds sometimes carry seeds great distances.

Any answer making it somewhat more likely that seabirds were responsible for the dispersal of Hawaiian seeds to the mountain regions of Reunion Island will strengthen the argument. This is our prephrase.

Answer choice (A): This is a Weaken answer, because it suggests a way the seeds could've floated across the ocean without becoming soaked in seawater, and makes it slightly more likely that a cause other than seabirds was responsible for the seed transfer.

Answer choice (B): This is the correct answer choice. The answer choice adds two things to the argument. A bird species common to Hawaii and Reunion makes it somewhat more likely that there are birds who fly between the two islands who could spread the seed species. The fact that bird is mountain-nesting strengthens the idea that the seeds they could've carried would've made it into the mountains of Reunion.

Answer choice (C): In an argument limited to explaining how A. koa could've been the ancestor to A. heterophylla, we do not benefit from any information about the ancestor to A. koa. Thus, this answer choice has no impact on the argument.

Answer choice (D): This answer choice is irrelevant, because it does not change the fact that seeds soaked in seawater cannot germinate. Thus it makes it no more or less likely that floating seeds from Hawaii became the tree species on Reunion.

Answer choice (E): The only possible effect of this answer choice is to weaken the argument, because it suggests that there are a number of seabird species that do not return to land frequently.

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