2. 外语
  3. In Asia, where palm trees are non-native, the trees’ flowers have traditionally been pollinated by hand, which has kept palm fru

In Asia, where palm trees are non-native, the trees’ flowers have traditionally been pollinated by hand, which has kept palm fru

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问题 In Asia, where palm trees are non-native, the trees’ flowers have traditionally been pollinated by hand, which has kept palm fruit productivity unnaturally low. When weevils known to be efficient pollinators of palm flowers were introduced into Asia in 1980, palm fruit productivity increased— by up to fifty percent in some areas—but then decreased sharply in 1984 . Which of the following statements, if true, would best explain the 1984 decrease in productivity?
选项 A、Prices for palm fruit fell between 1980 and 1984 following the rise in production and a concurrent fall in demand.
B、Imported trees are often more productive than native trees because the imported ones have left behind their pests and diseases in their native lands.
C、Rapid increases in productivity tend to deplete trees of nutrients needed for the development of the fruit-producing female flowers.
D、The weevil population in Asia remained at approximately the same level between 1980 and 1984.
E、Prior to 1980 another species of insect pollinated the Asian palm trees, but not as efficiently as the species of weevil that was introduced in 1980.
答案C
解析 如果(C)是正确的，1980年后亚洲棕榈树产量的迅速提高耗尽了培育果实的雌花生长需要的营养物质，因此(C)解释了为什么棕榈的产量随后下降，即(C)为正确答案；选项(A)将棕榈果实价格的下降与产量的增加和需求的下降联系起来，但没有解释随后该树产量的下降；选项(B)没有给出这些引入亚洲的树产量下降的原因；(D)也没有，因为(D)中描述的象鼻虫数量的稳定应支持在1980年到1984年之间棕榈树果实产量的稳定，而不是下降；因为(E)描述了1980年以前该树的授粉情况，它没有解释发生在1984年的变化
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