单选题
The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, (51) this is largely because, unlike animals, we stand upright. This means that our noses are (52) to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, (53) , we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of (54) human smells 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, (55) others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate (56) smell receptors in the nose. These receptors are the cells which sense smells and send (57) 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 (58) to it often enough. The explanation for insensitivity to smell seems to be that the brain finds it (59) to keep all smell receptors working all the time but can (60) new receptors if necessary.
单选题
A. although B. as C. but D. while
【正确答案】
C
【答案解析】[解析] 本题考查逻辑关系。空格前面的句子陈述了一种普遍存在的看法：“和动物相比，人类的嗅觉不灵敏”；空格后面部分则是在比较人类和动物的差异，指出：这只不过是因为人是直立的。这说明，前后句子的意思对应，所以空格处应该填入表示转折关系的词。A．although表示让步。B．as表示原因，在语文上与this is largely because重复。C．but表示转折。D．while有时相当于although，显然不对；有时表示转折，常用来表示同一事件相对的两个方面，而空格前后的句子不是对比关系，所以也不对。只有C．but符合句意。
单选题
A. limited B. committed C. dedicated D. confined
【答案解析】[解析] A．sign：标志，指显示事实、情况或性质在场或存在的某物，例：There are no signs of life about the house．这房子没有有人住的迹象。B．stimulus：刺激因素，指能引起或被认为引起反应的东西，例：Light is a stimulus to growth in plants．光是植物生长的促进因素。C．message：信息，指以书面、信号或其他方式从一个人、一个地方或一群人传给另一人、另一个地方或另一群人的消息，例：I have sent mot：her a message to tell her I shall be home late．我已经给母亲捎了个信儿，告诉她我回家晚点儿。D．impulse：本能，指驱动力或倾向。例：She bought the dress on impulse．她一时冲动买了这件衣服。只有“message”能够与“send”搭配使用。
【答案解析】[解析] A．introduce：推行，提倡，指引入到流通、使用或运行中。B．summon：召集，召唤，指要求出席或出现，例：The teacher summoned all the children to the room．老师把所有的孩子都叫进房间里。C．trigger：引发，触发，指导致……的产生，例：He accidentally triggered his rifle．他无意中扣发了他步枪的扳机。D．“create”对应后面的“new”一词。