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  3. Most people think of zoos as safe places for animals, where struggles such as difficulty finding food and avoiding predators (猛兽

Most people think of zoos as safe places for animals, where struggles such as difficulty finding food and avoiding predators (猛兽

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问题     Most people think of zoos as safe places for animals, where struggles such as difficulty finding food and avoiding predators (猛兽) don’t exist. Without such problems, animals in zoos should live to a ripe old age.
    But that may not be true for the largest land animals on Earth. Scientists have known that elephants in zoos often suffer from poor health. They develop diseases, joint problems and behavior changes. Sometimes, they even become infertile.
    To learn more about how captivity (圈养) affects elephants, a team of international scientists compared the life spans of female elephants born in zoos with female elephants living outdoors in their native lands. Zoos keep detailed records of all the animals in their care. These records made it possible for the researchers to analyze 40 years of data on 800 African and Asian elephants in zoos across Europe.
    The team found that female African elephants bora in zoos lived an average of 16.9 years. Their wild counterparts who died of natural causes lived an average of 56 years — more than three times as long. Female Asian elephants followed a similar pattern. In zoos, they lived 18.9 years, while those in the logging camps lived 41.7 years.
    Scientists don’t yet know why wild elephants seem to fare so much better than their zoo-raised counterparts. Georgia Mason, a biologist at the University of Guelph in Canada who led the study, thinks stress and obesity (肥胖) may be to blame. Zoo elephants don’t get the same kind of exercise they would in the wild, and most are very fat. Social lives of elephants are also much different in zoos than in the wild, where they live in large herds and family groups.
    Another finding from the study showed that Asian elephants born in zoos were more likely to die early than Asian elephants captured in the wild and brought to zoos. Mason suggests stress in the mothers in zoos might cause them to have babies that are less likely to survive.
    The study raises some questions about acquiring more elephants to keep in zoos. While some threatened and endangered species living in zoos reproduce successfully and maintain healthy populations, that doesn’t appear to be the case with elephants. "Currently, zoos are net consumers of elephants, not net producers," Mason says.
What is one of the possible reasons for the zoo-raised elephants’ problems?
选项 A、They do not get proper food.
B、They have to take intense exercise.
C、They do not live in family groups.
D、They are forced to reproduce babies.
答案C
解析 根据题干中的possible reasons将本题出处定位到第5段最后两句。这两句具体说明动物园大象出现问题的两个可能的原因：动物园里的大象不像野生大象那样活动，因此大多数都非常肥胖。大象在动物园里的社会生活也与在野外的很不同，在野外，大象过着群居的生活。[C]“它们没有过群居生活”与第二个原因对应，故为答案。[A]和[D]在文中未提及，故排除。由文中提到的“动物园里的大象不像野生大象那样活动，因此大多数都非常肥胖”可推知，动物园的大象的活动强度很低，故排除[B]。
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