Explanation
Correct answer: C.
Choice C is the best answer because it most accurately describes the main purpose of the text, which is to describe the family of plants known as the silversword alliance and explain why the plants came to exhibit "an extraordinary range of phenotypes." The text introduces the silversword alliance as a family of plants unique to the Hawaiian Islands, presenting those that mature into vines and those that mature into shrubs and trees as examples of different phenotypes. The text concludes by explaining that these plants are all descendants of "a single ancestral tarweed plant" that arrived 5 million years ago in the Hawaiian Islands, where a "wide variety of habitats" drove the plant’s descendants to adapt and thus differentiate themselves, diversifying into a group of related but distinct species with different physical characteristics.
Why the other choices are wrong
Choice A
Choice A is incorrect. Although the text explains why the plants within the silversword alliance have varied physical characteristics, the text doesn’t suggest that tarweed is the ancestor of all plants on the Hawaiian Islands. The text states instead that all members of the silversword alliance descend from a single tarweed ancestor.
Choice B
Choice B is incorrect because while Dubautia carrii is mentioned as an example of a species in the silversword alliance, no details about its particular habitat are provided. And although the text indicates that the Hawaiian Islands are home to "a wide variety of habitats," it doesn’t describe the specific habitat where Dubautia carrii is found. The text discusses the silversword alliance as a whole rather than focusing on Dubautia carrii or any one species within this family.
Choice D
Choice D is incorrect. Although the silversword alliance is only found on the Hawaiian Islands and includes "an extraordinary range of phenotypes," the text doesn’t claim that all plants on the Hawaiian Islands are part of the alliance. Furthermore, the text indicates that these plants all "descended from a single ancestral tarweed plant," not that there are multiple possible candidates for that ancestor plant.
Student discussion
marcosat 0 likes
The answer is C because the other options are largely wrong. A) assumes that all plants in the hawaiian island came from the given ancestor. B) It does not talk about habitat at all. D) Not all plants are from the alliance. Wrong.