求问几道阅读机经题

GRE阅读机经200篇里的 Passage 192 In an experiment, a group of pregnant mice were each given food containing minute doses of the hormone BPA. A control group of pregnant mice were given no BPA. Offspring of mothers that had been given BPA were 10 percent bigger when weaned from their mothers than were offspring of mothers in the control group. Clearly, this result supports the hypothesis that the physical development of mice is significantly affected by prenatal exposure to BPA. Which of the following is an assumption on which the argument depends? A. Prenatal exposure of mice to doses of BPA even smaller than those used in the experiment would not have significantly affected the physical development of the mice. B. At birth, there was no difference in size between offspring of mothers that had been given BPA and offspring of mothers in the control group. C. Postnatal exposure of mice to BPA before the mice are weaned has significant effects on the physical development of the mice. D. Exposure of a pregnant mouse to the doses of BPA used in the experiment does not significantly enhance its ability nurse its offspring. E. Significant differences in size between offspring of mothers that had been given BPA and offspring of mothers in the control group persisted long after the offspring were weaned 给的答案选B，但是我怎么都觉得D要更加对一些。求问大大们这个实验到底要控制什么变量呢？ Passage 194 Unlike herbivores and omnivores, predators have traditionally been thought not to balance nutrient intake because of the assumption that animal tissue as a food source varies little and is nutritionally balanced. But chemical analysis of invertebrate prey reveals remarkable variation in nutrient composition among species; even within species, nutrient composition may vary considerably. Greenstone suggested that predators may select food items according to their nutrient contents. Jensen et al (2011) have shown experimentally that even sit-andwait invertebrate predators with limited mobility can work to address nutrient deficiencies. The wolf spider, for instance, has been shown to regulate nutrient intake by extracting more dry mass from a prey item if it contains a higher proportion of a nutrient that was deficient in the previous prey. 2. Which of the following best describes the organization of the passage as a whole? A. A phenomenon is described, and an interpretation is offered. B. A claim is made, and the corroborating evidence is evaluated. C. A hypothesis is presented and undermined by recent findings. D. A contrast is noted and shown to be specious based on recent findings. E. A series of assumptions is presented and shown to be based on sound reasoning. 给的答案选C，一直搞不太懂这类题目，什么样的陈述才叫hypothesis呢？感觉这道题目中第一句并不是个hypothesis。