96-08第三篇阅读百思不得其解，麻烦大家给看看

Grows 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.

  Grows 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 adapt 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, who are among the wariest and most untrappable of birds.

  Technical difficulties aside, crow research is daunting because the ways of the 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 scams. 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.

想知道大家得选项

c,

d,

c,

b,

b,

a,

d

Grows 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 adapt at avoiding them.

这个我犹豫了一下。 你看整个句子。

Grows 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.>>

  Grows 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 adapt at avoiding them.[27A] Because they are so numerous, active, and monochromatic, it is difficult to distinguish one crow from another.[27B] Bands, radio transmitters, or other identifying devices can be attached to them, but this of course requires catching live crows, who are among the wariest and most untrappable of birds.[27D]>>

  Technical difficulties aside, crow research is daunting because the ways of the 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 scams. 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.

网速实在太慢了，发完才发现Brace早就贴了答案，强烈支持Brace的答案以及对them指代题的解释。
那我下载的所谓修订过的正确答案到底是什么来源呢？为什么这篇文章的答案看着这么不像正确的？