托福考试

【单选题】Naturalists and casual observers alike have been struck by the special relationship　　　 between squirrels and acorns (the seeds of oak trees).Ecologists, though, cannot observe　　　 These energetic mammals scurrying up and down oak trees and eating and burying acorns　　　 without wondering about their complex relationship with trees.Are squirrels dispersers(5) 　and planters of oak forests or pesky seed predators The answer is not simple. Squirrels　　　 may devour many acorns, but by storing and failing to recover up to 74 percent of them　　　 (as they do when seeds are abundant), these arboreal o\rodents can also aid regeneration　　　 and dispersal of the oaks.　　　 Their destructive powers are well documenteD、According to one report, squirrels(10)　 destroyed tens of thousands of fallen acorns from an oak stand on the University of　　　 Indiana campus.
A、professor there estimated that each of the large while oaks haD、　　　 Produced between two and eight thousand acorns, but within weeks of seed maturity,　　　 Hardly an intact acorn could be found among the fallen leaves.　　　 Deer, turkey, wild pigs, and bears also feed heavily on acorns, but do not store them,(15)　And are therefore of no benefit to the trees. Flying squirrels, chipmunks, and mice are　　　Also unlikely to promote tree dispersal---whose behavior of caching (hiding) acorns below　　　 The leaf litter often promotes successful germination of acorns---and perhaps blue jays,　　　 Important long-distance dispersers, seem to help oaks spread and reproduce.　　　 Among squirrels, though, there is a particularly puzzling behavior pattern. Squirrels(20)　 pry off the caps of acorns, bite through the shells to get at the nutritious inner kernels,　　　 and then discard them half-eaten. The ground under towing oaks is often littered with　　　 thousands of half-eaten acorns, each one only bitten from the top. Why would any animal　　　 waste so much time and energy and risk exposure to such predators as red-tail hawks only　　　 to leave a large part of each acorn uneaten While research is not conclusive at this point,(25)　 one thing that is certain is that squirrels do hide some of the uneaten portions, and these　　　 acorn halves, many of which contain the seeds, may later germinate.The word "they" in line 7 refers to
A、oak forests
B．acorns
C．squirrels
D．predators

网考网参考答案：B
网考网解析：
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