全国硕士研究生入学统一考试---英语2005年试题及解析

（单词翻译:单击）

2005年全国硕士研究生入学考试英语试题及答案 

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 genes¹ necessary to generate² (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 the 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 unfamiliar³ and emergency signals (20) ____ the smell of smoke, which might indicate the danger of fire. 

1. [A] although 
[B] as 
[C] but