20XX年全国硕士研究生入学统一考试英语试题
Section I: Use of English
Directions:
Read the following text. Choose the best word(s) for each numbered blank and mark [A], [B], [C] or [D] on ANSWER SHEET 1 (10 points)
The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, __1__ this is largely because, __2__ animals, we stand upright. This means that our noses are __3__ to perceiving those smells which float through the air, __4__ the majority of smells which stick to surfaces. In fact, __5__, we are extremely sensitive to smells, __6__ we do not generally realize it. Our noses are capable of __7__ human smells even when these are __8__ to far below one part in one million.
Strangely, some people find that they can smell one type of flower but not another, __9__ others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate __10__ smell receptors in the nose. These receptors are the cells which sense smells and send __11__ to the brain. However, it has been found that even people insensitive to a certain smell __12__ can suddenly become sensitive to it when __13__ to it often enough.
The explanation for insensitivity to smell seems to be that brain finds it __14__ to keep all smell receptors working all the time but can __15__ new receptors if necessary. This may __16__ explain why we are not usually sensitive to our own smells we simply do not need to be. We are not __17__ of the usual smell of our own house but we __18__ new smells when we visit someone else’s. The brain finds it best to keep smell receptors __19__ for unfamiliar and emergency signals __20XX the smell of smoke, which might indicate the danger of fire.
1. [A] although
[B] as
[C] but
[D] while
2. [A] above
[B] unlike
[C] excluding
[D] besides
3. [A] limited
[B] committed
[C] dedicated
[D] confined
4. [A] catching
[B] ignoring
[C] missing
[D] tracking
5. [A] anyway
[B] though
[C] instead
[D] therefore
6. [A] even if
[B] if only
[C] only if
[D] as if
