Crows are probably the most frequently met and easily identifiable members of the native fauna of the United States. The great n

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问题     Crows are probably the most frequently met and easily identifiable members of the native fauna of the United States. The great number of tales, legends, and myths about these birds indicates that people have been exceptionally interested in them for a long time. On the other hand, when it comes to substantive — particularly behavioral — information, crows are less well known than many comparably common species and, for that matter, not a few quite uncommon ones: the endangered California condor, to cite one obvious example. There are practical reasons for this.
    Crows are notoriously poor and aggravating subjects for field research. Keen observers and quick learners, they are astute about the intentions of other creatures, including researchers, and adept at avoiding them. Because they are so numerous, active, and monochromatic, it is difficult to distinguish one crow from another. Bands, radio transmitters, or other identifying devices can be attached to them, but this of course requires catching live crows, which are among the wariest and most untrappable of birds.
    Technical difficulties aside, crow research is daunting because the ways of these birds are so complex and various. As preeminent generalists, members of this species ingeniously exploit a great range of habitats and resources, and they’ can quickly adjust to changes in their circumstances. Being so educable, individual birds have markedly different interests and inclinations, strategies and seams. For example, one pet crow learned how to let a dog out of its kennel by pulling the pin on the door. When the dog escaped, the bird went into the kennel and ate its food.
According to the second paragraph,  crows are poor subjects for field research for all the following reasons EXCEPT ______.

选项 A、they can successfully avoid observers
B、they are hard to distinguish from one another
C、they can be quite aggressive
D、they are difficult to catch

答案C

解析 细节定位题。 根据第2段的内容运用排除法,A项:它们能成功地逃避观察;B项:很难辨认它们的不同,C项;它们很好斗,D项;它们很难抓。其中选项A,B,D都有提到,唯独选项C没有提到,故C项正确。
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