The mimosa tree evolved in East Asia, where the beetle Bruchidius terrenus preys on its seeds. In 1785, mimosa trees were
introduced to North America, far from any B. terrenus. But evolutionary links between predators and their prey can persist
across centuries and continents. Around 2001, B. terrenus was introduced in southeastern North America near where
botanist Shu-Mei Chang and colleagues had been monitoring mimosa trees. Within a year, 93 percent of the trees had been
attacked by the beetles.
It states the hypothesis that Chang and colleagues had set out to investigate using mimosa trees and B. terrenus.
It presents a generalization that is exempliﬁed by the discussion of the mimosa trees and B. terrenus.
It provides context that clariﬁes why the species mentioned spread to new locations.
It offers an alternative explanation for the ﬁndings of Chang and colleagues.
Choice B is the best answer because it most accurately describes the function of the third sentence within the overall
structure of the text. The third sentence makes a generalization, asserting that evolutionary links between predators and prey
can persist across great expanses of time and distance. This generalization is exempliﬁed by the text’s discussion of the
relationship between mimosa trees and B. terrenus beetles. When mimosa trees were introduced to North America in 1785,
no B. terrenus beetles were present, so the relationship between the trees and the beetles that exists in their native East Asia
was disrupted. When the beetles were introduced to North America more than 200 years later, however, they quickly attacked
mimosa trees, illustrating the generalization that links between predators and prey "can persist across centuries and
continents."
Choice A is incorrect because the third sentence doesn’t indicate that Chang and colleagues were investigating any
hypothesis. According to the text, Chang and colleagues were simply monitoring mimosa trees when the beetles happened
to be introduced to the area. Choice C is incorrect because the third sentence doesn’t discuss any particular species, let
alone the species mentioned elsewhere in the text, nor does the sentence explain why species spread to new locations.
Choice D is incorrect because the third sentence offers a generalization about the relationship between predators and prey,
not an explanation for the ﬁndings by Chang and colleagues that’s an "alternative" to an explanation presented elsewhere in
the text.