2. 外语
  3. A. limited B. distinguish C. unlike D. particular E. trigger F. inefficient G. create H. emergency I. incompetent J. detecting K

A. limited B. distinguish C. unlike D. particular E. trigger F. inefficient G. create H. emergency I. incompetent J. detecting K

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问题 A. limited B. distinguish C. unlike D. particular E. trigger
F. inefficient G. create H. emergency I. incompetent J. detecting
K. aware L. messages M. unusual N. surfaces O. confined
   The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, but this is largely because,【C1】______ animals, we stand upright. This means that our noses are【C2】______ to perceiving those smells which float through the air, missing the majority of smells which stick to【C3】______. In fact, though, we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of【C4】______ human smells even when these are diluted to far below one part in one million.
   Strangely, some people find that they can smell one type of flower but not another, whereas others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate【C5】______ smell receptors in the nose. These receptors are the cells which sense smells and send【C6】______ to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when exposed to it often enough.
   The explanation for insensitivity to smell seems to be that the brain finds it【C7】______ to keep all smell receptors working all the time but can【C8】______ new receptors if necessary. This may also explain why we are not usually sensitive to our own smells-we simply do not need to be. We are not 【C9】______ of the usual smell of our own house, but we notice new smells when we visit someone else’s. The brain finds it best to keep smell receptors available for unfamiliar and【C10】______ signals such as the smell of smoke, which might indicate the danger of fire.
【C4】
选项
答案J
解析 空格前的of和其后的名词短语提示，此处填入动词的现在分词形式。此处空格用来描述在某种条件下，我们的鼻子能对气味做出怎样的反应。前面说到我们的嗅觉是十分灵敏的，由此推断此处说的是人身上的各种不同气味即使被稀释到远不及原来的百万分之一，我们的鼻子也能够觉察到。detecting“发现，察觉出”符合题意。distinguish表示“区别；辨别出”，但此处并非讨论鼻子可以分辨出不同气味的功能，而只是描述鼻子可以感知某种气味。
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