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  3. Across the western United States alone, trout (a kind of fish) fishing generates hundreds of millions of dollars annually. But t

Across the western United States alone, trout (a kind of fish) fishing generates hundreds of millions of dollars annually. But t

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问题    Across the western United States alone, trout (a kind of fish) fishing generates hundreds of millions of dollars annually. But trout habitat will likely be cut in half by 2080 due to warming rivers and altered patterns of flooding, according to a large study published online in the Proceedings of the National Academy of Sciences, "It’s fairly shocking to us, as biologists," says co-author Kurt Fausch of Colorado State University, Fort Collins. This is not a case of winners and losers; the four species examined by the team are all likely to decline to varying degrees.
   By running several climate models and plugging in data on habitat characteristics and fish present at 9,890 locations in the Rocky Mountains and Great Basin, the team of scientists created predictions for trout habitat across more than 1 million square kilometers of the western United States. They factored physical aspects of habitat—water temperature, patterns of flooding—as well as competition among species. Here’s what the study concludes about the future of trout:
   Increases in water temperature will restrict their range, but rainbow trout dodge a bullet. Climate change will mean more frequent and intense winter floods, which can scour away eggs laid in the fall, but rainbow trout spawn in the spring. The size of their habitat is predicted to decline by 35%.
   Smaller than rainbow trout, brown trout are the most temperature tolerant among the four species and like warmer temperatures. They have the ill fortune to spawn in the fall, so the increased flooding will make many streams inhospitable. Their habitat is predicted to decline by 48%.
   As to cutthroat trout, the range of these native fish has already shrunk by more than 85% due to competition from introduced species. Two subspecies have already gone extinct. Wanning temperatures and continued competition primarily from rainbow trout are predicted to reduce suitable habitat by a further 58%.
   Compared with the other species, brook trout are the biggest losers in 2080. Because they spawn in the fall, the increase in winter flooding is expected to reduce their suitable habitat by 77%—a surprising amount given their success at invading new habitat.
   Frank Rahel, a fish ecologist at the University of Wyoming in Laramie, says the findings help paint the big picture for trout this century.
   "They’re very sobering results that will catch people’s attention," he says. Not much can be done to reduce the impact of winter floods, but managers already try to keep streams cooler by planting trees and shrubs.
   
What’s the prediction on the habitat of trout based on?
选项 A、The presence of fish in different habitats of trout.
B、A scientific simulation including various factors.
C、The field work of a team of scientists.
D、The characteristics of the west part of America.
答案B
解析 细节题。根据题干关键词定位到第二段第一句，由此可知，通过运行若干气候模型、嵌入栖息地特征的数据以及9 890处落基山脉和大盆地的鳟鱼出没情况，科学家们对美国西部超过100万平方公里范围的鳟鱼的栖息地做出了预测。由此可知，对鳟鱼栖息地的预测是建立在对若干因素进行模拟的方式上的，因此B项与原文意思相符，是正确答案。
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