OG9 阅读 Q21

Choice A is the best answer. Throughout the passage, the author describes experiments conducted on guppies to determine the guppies' rate of and types of evolutionary change. The first paragraph outlines the reason why these fish were an optimal choice for this research: their "unstinting rate of reproduction makes guppies ideally suited for studying the rate of evolution." Therefore, the first paragraph mainly serves to establish the reason why a certain species was selected for scientific observation.
Choice B is incorrect because the purpose of the first paragraph isn't to illustrate the value of studying the offspring of a particular animal shortly after birth. Instead, guppies were selected because of their rapid rate of reproduction and weren't only studied shortly after being born, according to the passage. Choices C and D are incorrect. Although the fourth paragraph does introduce a new method of scientific inquiry (experimental evolution), the first paragraph doesn't mainly serve to introduce a theory at the center of an ongoing scientific debate (choice C) or offer a rationale for the prevalence of a new field of scientific inquiry (choice D).