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

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

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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【S1】______to wander about the African, Eurasian, and American continents. Today, only two【S2】______of elephants are left in South Asia and Africa. One theory for his dramatic death holds that rapid climate shifts at the end of the most recent major ice age, some 10,000 years ago,【S3】______vegetation and broke up habitats (栖息地), causing the death of those unable to adapt to the new conditions. Another【S4】______blames prehistoric humans, whose improved weapons and hunting techniques  allowed them to wipe out whole herds of elephants.
    To help【S5】______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【S6】______regions should match human expansion into those regions. On the contrary, if the extinction was【S7】______to climate change, elephants should remain in regions【S8】______colonized by humans and would only begin to die off once climate change occurred.
    The team tested both theories by analyzing where and whet1 elephants were killed. In all, the study included 41 archaeological sites on five continents. The researchers found that, as humans【S9】______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. Modem elephants survived in refuges【S10】______to humans, such as tropical forests, says Surovell.

A) uninviting          B) migrated          C) used             D) due  
E) mysterious          F) specific          G) already          H) casually
I) hypothesis          J) endurance         K) resolve          L) polish
M) altered             N) declined          O) species
【S4】
选项
答案I
解析 此处应该是可数名词单数，做主语。hypothesis是可数名词单数。another hypothesis与前句中的主语one theory形成并列关系。
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