Explanation
Correct answer: D.
Choice D is the best answer because it most logically completes the text’s discussion of conservation approaches for the Mammillaria cactus M. boolii. The text establishes that M. boolii only grows naturally in the state of Sonora in Mexico, which makes it particularly vulnerable to extinction. The text then contrasts two approaches to conservation: the traditional single-species approach that individually focuses on at-risk species and a newer ecosystem-based approach that considers the interactions between climate, terrain, and various species in a geographical area. According to the text, conservationists have recently argued that this ecosystem-based approach may lead to better outcomes for all species in a location. If this ecosystem view is correct, then the single-species approach to conserving M. boolii would likely fail to consider how the cactus’s survival depends on its interactions with other species in Sonora’s ecosystem.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text doesn’t address the distribution of Mammillaria species besides M. boolii throughout Mexico or discuss how that distribution affects survival. The text focuses specifically on M. boolii in Sonora and different approaches to its conservation.
Choice B
Choice B is incorrect because the text doesn’t suggest that climatic changes in Sonora would reduce competition for M. boolii or that conservation efforts are focused on understanding this specific dynamic. In fact, the text implies that an ecosystem-based approach would consider climate among many other factors but doesn’t specify how climatic changes might affect competition between species.
Choice C
Choice C is incorrect because the text doesn’t suggest that the single-species approach would shift the focus of conservation efforts away from M. boolii itself—rather, it suggests that this approach might be too narrowly focused on M. boolii alone without considering the broader ecosystem-related factors that affect its survival.