Noting that bison herds appear to graze selectively in areas occupied by prairie dog colonies, Coppock hypothesized that the att

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问题     Noting that bison herds appear to graze selectively in areas occupied by prairie dog colonies, Coppock hypothesized that the attraction is due to improved forage quality: prairie dogs’ own grazing activities alter herbage dynamics, plant species composition, and nutrient cycling. The colonies’ territory contains relatively little low-quality mature standing herbage and is characterized by communities of plants that are high in crude protein and highly digestible. However, such effects are not produced only by prairie dogs. Willms showed that sites selectively grazed by cattle had reduced standing dead plant material, altered species composition, and increased soil nitrates, ammonium, and available phosphorus. In fact, long-term, intensive use by any grazer will cause comparable changes in plant communities.
The highlighted sentence serves primarily to

选项 A、provide information about the kinds of forage preferred by prairie dogs
B、refute a particular claim about the forage methods of prairie dogs
C、specify what makes forage conditions created by prairie dogs appealing to bison
D、suggest that prairie dogs’ activities can cause environmental degradation
E、identify characteristics that influence prairie dogs’ selection of sites to colonize

答案C

解析 本题属于功能题,定位句是例子,用于说明土拨鼠具体做了哪些改变使得这片土地能够吸引野牛,因此选项C正确。
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本试题收录于: GRE VERBAL题库GRE分类
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