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  3. More boys than girls are born all over the world, but a new study has found that the closer people live to the equator(赤道), the

More boys than girls are born all over the world, but a new study has found that the closer people live to the equator(赤道), the

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问题     More boys than girls are born all over the world, but a new study has found that the closer people live to the equator(赤道), the smaller the difference becomes. No one knows why.
    The imbalanced sex ratio at birth has been known for more than a hundred years, and researchers have found a large variety of social, economic and biological factors that relate to the sex ratio at birth—war, economic stress, age, diet, selective abortion and more. But latitude(纬度)is a natural phenomenon, unaffected by cultural or economic factors.
    To look at the effect of latitude, Kristen J. Navara of the University of Georgia used the latitude of the capital city in 202 countries, as well as 10 years of data on sex ratio at birth and annual variations in day length and temperature. Dr. Navara performed a statistical analysis which showed that there was a significant relation between sex ratios in favor of boys and latitude. African countries produced the lowest sex ratios—50. 7 percent boys—and European and Asian countries had the highest with 51. 4 percent.
    There are some possible explanations, but none entirely satisfactory. It could be that there is some survival value in producing more girls in warmer regions, but it is unclear what this might be. There may be genetic or racial differences that could explain it, but the connection persists over so many varied populations that this seems unlikely. Mice also produce more male offspring during shorter days or colder weather, but the reasons in these animals are just as mysterious as they are in humans.
    "There’s a possibility that humans might be responding to factors they were programmed to respond to a long time ago—not cultural or socioeconomic, but climate and things like latitude," Dr. Navara said. "What’s interesting is that we may be seeing something that connects us with our animal ancestry. "
According to Navara, which of the following probably explains the imbalanced sex ratio?
选项 A、There is cultural preference for boys.
B、Humans are designed that way by nature.
C、Different races have different birth ratios.
D、Humans are different from animals in birth ratio.
答案B
解析 此题是一道细节推断题，考查考生根据文章中的相关重点细节内容进行分析推断得出结论的能力。问题问按照纳瓦拉博士的观点，下面哪种说法可能解释性别比例失衡。文章最后一段指出：“有一种可能性，即人类可能会对一些因素做出反应，而这些因素是人类很久以前就已程序化来做出反应的因素——不是文化因素或社会经济因素，而是气候和纬度之类的东西，”纳瓦拉博士说，“有趣的是，我们可能会看到将我们人类与我们的动物祖先联系在一起的某种东西。”由此我们可以判断出本题的答案应该是B，人类天生就是这么设计的。选项A：在文化方面对男孩存在偏爱，文章没有提到；C：不同的民族有不同的出生率，原文对此进行了否定的评价；D：人类与动物在出生率上有所不同，与原文最后一句话不符。因此这三个选项均为干扰项。
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