Explanation:

1. B
Given the description of the passage above, it is clear that Choice B is correct: the passage focuses on “different theories about the transport of plant seeds to Hawaii.” Choice A can be eliminated: while the passage does refer to flotation experiments, it does not elaborate on experimental methods. Choice C identifies an idea that is part of the passage’s main concern, but since this is only one of the competing theories discussed in the passage, not the primary focus, Choice C is incorrect. Choices D and E are incorrect because the passage does not resolve any disputes.

2.D
This question asks why the author mentions flotation experiments. Flotation experiments are mentioned in the passage in order to show that some evidence casts doubt on the claim that ocean currents were the means by which seeds were transported to Hawaii. Thus, Choice D is correct. Choice A is incorrect since the claim that plant distribution in Hawaii is the result of long-distance dispersal of seeds is a given in the passage, not an idea that the author feels a need to substantiate. Choice B is eliminable since the flotation experiments are introduced at a point where the author is challenging, rather than lending credibility to, the air current hypothesis and because flotation experiments would more likely reflect on ocean currents than air currents. Choice C is
eliminable since the passage does not address the length of time required for longdistance seed dispersal. Finally, Choice E is eliminable since it too describes an idea that is not discussed in the passage.
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