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  3. Hungry prehistoric hunters, not climate change, drove elephants to extinction during the Pleistocene era (更新世), new research sug

Hungry prehistoric hunters, not climate change, drove elephants to extinction during the Pleistocene era (更新世), new research sug

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问题     Hungry prehistoric hunters, not climate change, drove elephants to extinction during the Pleistocene era (更新世), new research suggests.
    At least 12 kinds of elephants【C1】______to wander about the African, Eurasian, and American continents. Today, only two【C2】______of elephants are left in South Asia and Africa. One theory for this dramatic death holds that rapid climate shifts at the end of the most recent major ice age, some 10,000 years ago,【C3】______vegetation and broke up habitats (栖息地), causing the death of those unable to adapt to the new conditions. Another【C4】______blames prehistoric humans, whose improved weapons and hunting techniques allowed them to wipe out whole herds of elephants.
    To help【C5】______the debate, archaeologist Todd Surovell of the University of Wyoming, and colleagues tested two assumptions. If humans caused the elephant extinction, Surovell reasoned, the timing of the die-off in【C6】______regions should match human expansion into those regions. On the contrary, if the extinction was【C7】______to climate change, elephants should remain in regions【C8】______colonized by humans and would only begin to die off once climate change occurred.
    The team tested both theories by analyzing where and when elephants were killed. In all, the study included 41 archaeological sites on five continents. The researchers found that, as humans【C9】______out of Africa, they left a trail of dead elephants behind them. The creatures disappear from the fossil record of a region once it became colonized by humans. Modern elephants survived in rerfuges【C10】______to humans, such as tropical forests, says Surovell.
    A. uninviting B. migrated C. declined D. due
    E. memorial F. specific G. already H. casually
    I. hypothesis J. endurance K. resolve L. polish
    M. altered N. used O. species
【C1】
选项
答案N
解析 此处需要能跟不定式词to的动词作谓语的一部分。从词库中的六个动词来看，used与to搭配，意为“过去常常”，与后一句的Today形成对比，故为答案。
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