OG详解-OG5 文法 Q14

Choice D is the best answer. The sentence effectively indicates the California red-legged frog’s FWS classification category, noting that the FWS classifies the frog as threatened, a classification given to species that are likely to soon become endangered.
Choice A is incorrect. The sentence specifies the classification categories of the FWS list; it doesn’t indicate the classification category of the California red-legged frog. Choice B is incorrect. While the sentence does note that the California red-legged frog is among the species classified by the FWS, it doesn’t indicate what classification category the California red-legged frog occupies. Choice C is incorrect. While the sentence does appear to indicate the California red-legged frog’s FWS classification category, the sentence is factually incorrect and therefore ineffective; the frog’s classification category is threatened, not endangered.