The Canadian elk has traditionally been limited in its geographic range by the presence of elderberries, its primary source of food, which only grow up until a certain point in the tundra. A recent rise in temperatures, however, has seen a spread in the growth of elderberries northwards into the tundra. Therefore, the overall range of the Canadian elk can be expected to increase.
Which of the following, if true, best casts doubt on the argument?
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AIn addition to elderberry, the Canadian elk also consumes loganberries, which are expected to also begin growing at more northerly latitudes.
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BDuring the summer months, many Canadian elk are hunted both for sport and for their meat.
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CThe grizzly bear, the Canadian elk's primary predator, has also started moving north into the tundra.
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DThe permafrost, the region above the tundra, in which the temperatures never reach above freezing, will unlikely see elderberry growth.
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EIncreasing temperatures have created conditions too warm for elderberry growth in the southern half of the Canadian elk's traditional territory.
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正确答案: E