OG9 阅读 Q22

Choice B is the best answer. The third sentence of the second paragraph states, "A lucky guppy is born above a waterfall or a set of rapids, which keep out the predatory fish called pike cichlids found in calmer downstream waters." In other words, pike cichlids normally eat guppies, but waterfalls and rapids can create natural barriers that prevent these predators from entering certain areas where guppies live. Thus, in describing the living conditions of guppies, the author indicates that a "lucky guppy" is one that inhabits an environment that provides natural protection from predators.
Choices A and C are incorrect because the author doesn't indicate that being born in a major river with an established guppy population is an advantage for a guppy (choice A) or that there are risks associated with living near a waterfall or that guppies benefit by avoiding such risks (choice C). Choice D is incorrect because the author doesn't indicate that there is an advantage for guppies living in calmer downstream waters. Instead, the author notes that calmer downstream waters are where guppies' predators live, making these zones more dangerous for guppies than the areas above waterfalls or rapids.