2. 外语
  3. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because______ Ac

According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because______ Ac

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问题 According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because______
According to the passage, which of the following best describes a function performed by oligosaccharins?
选项 A、Regulating the daily functioning of a plant’s cells
B、Interacting with one another to produce different chemicals
C、Releasing specific chemical messengers from a plant’s cell walls
D、Producing the hormones that cause plant cells to differentiate to perform different functions
E、Influencing the development of a plant’s cells by controlling the expression of the cells’ genes
答案E
解析 The best answer is E. The first paragraph states that plant cells “differentiate and form structures” (line 3) when a “complex system of chemical messengers” (line 7) activates a “small subset of the genes in a particular kind of cell” (lines 5-6). In lines 38-41, the author elaborates on the hormonal system in plants by indicating that the pleiotropic plant hormones activate enzymes, which in turn release oligosaccarins-the “more specific chemical messengers” (lines 40-41). The second paragraph indicated these specific chemical messengers have specific effects on plant development. Thus, the passage indicates that it is the oligosaccharins that directly influence the development of a plant cell by controlling the expression of a plant cell’s genes. Choices C and D are incorrect because the oligosaccharins are themselves specific chemical messengers and are not said to produce any hormones. The passage provides no information to support A or B.
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