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  3. The disappearance of Steller’s sea cow from the Bering and Copper islands by 1768 has long been blamed on intensive hunting. But

The disappearance of Steller’s sea cow from the Bering and Copper islands by 1768 has long been blamed on intensive hunting. But

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问题     The disappearance of Steller’s sea cow from the Bering and Copper islands by 1768 has long been blamed on intensive hunting. But its disappearance took only 28 years from the time Steller first described the species, a remarkably short time for hunting alone to depopulate the islands, especially given the large populations initially reported. However, by 1750, hunters had also targeted nearby sea otter populations. Fewer otters would have allowed sea urchin populations on which the otters preyed to expand and the urchins’ grazing pressure on kelp forests to increase. Sea cows were totally dependent on kelp for food, and within a decade of the onset of otter hunting, Steller noted that the islands’ sea cows appeared malnourished.
According to the passage, it is likely that during the mid-1700s, sea urchin populations near the Bering and Copper islands
选项 A、were diminished by sea cow predation
B、experienced substantial increases
C、migrated to waters with more plentiful food supplies
D、were reduced by the pressures of hunting
E、appeared to be malnourished
答案B
解析 根据文章，1700年代中期海胆的数量因为海獭数量锐减而增多，选项B正确。
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