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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

admin2017-06-11  54
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. "
What can be learned from the first paragraph?
选项 A、The closer to the equator, the more boys are born.
B、Boys are more used to colder places.
C、Girls have a higher birth rate than boys near the equator.
D、In warmer places the birth ratio between boys and girls is lower.
答案A
解析 主旨大意题。从原句“More boys than girls are born all over the world…thesmaller the difference becomes”可知．全世界男人多，女人少，但是离赤道近的地方，男女比例差别变得小了。选项A与第一段的内容相符。第一段没有提及男人习惯于住哪，B可被排除。第一段并没有提及birth rate和birth ratio问题，由此可排除C和D。
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