Sea Cow

　　The disappearance of Steller's sea cow from the Bering and Copper is lands by 1768 has long been blamed on intensive hunting. But its dis appearance took only 28 years from the time Steller first described the species, a remarkably short time for hunting alone to depopulate the is lands, especially given the large populations initially reported. However, by 1750, huntershad also targeted nearby sea otter populations . Fewer otters would have allowed s ea urchin

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　　populations on which the otterspreyed 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 is lands' sea cows appeared malnourished.

　　1. Which of the following can be inferred from the pas s age about kelp forests in the Bering

　　and Copper is lands between 1750 and 1768?

　　A. They were reduced significantly.

　　B. They disappeared entirely from the region.

　　C. They were the primary food source for sea otters .

　　D. They were harvested in record numbers by humans

　　E. They increased pressure on sea urchin populations.

　　2. According to the pas s age, it is likely that during the m id-1700s, s ea urchin populations

　　near the Bering and Copper is lands

　　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：AB