单选题 In the past few decades, remarkable findings have been made in ethology, the study of animal social behavior. Earlier scientists had (21) that nonhuman social life was almost totally instinctive or fixed by genetics. Much more careful observation has shown that (22) variation occurs among the social ties of most species, showing that learning is a part of social life. That is, the (23) are not solely fixed by the genes (24) , the learn ing that occurs is often at an early age in a process that is called imprinting. Imprinting is clearly (25) instinctive, but it is not quite like the learning of humans; it is something in between the two. An illustration best (26) the nature of imprinting. Once, biologists thought that ducklings followed the mother duck because of instincts. Now we know that, shortly (27) they hatch, ducklings fix (28) any object about the size of a duck and will henceforth follow it. So ducklings may follow a basketball or a briefcase if these are (29) for the mother duck at the time when imprinting occurs. Thus, social ties can be considera bly (30) , even ones that have a considerable base (31) by genetics.
Even among the social insects something like imprinting (32) influence social behav ior. For example, biologists once thought bees communicated with others purely (33) in stinct. But, in examining a "dance" that bees do to indicate the distance and direction of a pollen source, observers found that bees raised in isolation could not communicate effec tively. At a higher level, the genetic base seems to be much more for an all-purpose learn ing rather than the more specific responses of imprinting. Chimpanzees, for instance, gen erally (34) very good mother but Jane Goodali reports that some chimps carry the infant upside down or (35) fail to nurture the young.

单选题 A. than B. before C. when D. after

单选题 A. on B. with C. in D. within

单选题 A. appropriated B. substituted C. assigned D. distributed

【正确答案】 B

【答案解析】[解析] 此处可翻译为：“如果在‘印象’发生时，用篮球或公文包代替母鸭，小鸭子也许会跟随它们。”B项substituted意为“替代；调换(常与for连用)”，例如：substitu ted A for B，意为“用A代替B”。A项appropriated意为“拨给(款项等)供专用”，例如：The government appropriated a large sum of money for building schools．政府拨出一大笔钱修建学校。C项assigned意为“指派”；D项distributed意为“分发，分配”。只有B项符合题意，所以B为正确答案。

单选题 A. varied B. deviated C. differed D. altered

【正确答案】 D

【答案解析】[解析] D项alter意为“改变，更改”，相当于change，符合题意。A项vary意为 “变化，使不同(强调范围变化)”，vary from…to…意为“从……到……不等；在…… 到……之间”，例如：The temperature varies from time to time．温度常常变化。B项deviate意为“越出正轨，违反”。C项differ意为“使相异”。

单选题 A. fashioned B. modified C. influenced D. affected

【正确答案】 A

【答案解析】[解析] A项fashion在这里作动词，意为“构成，做成……形状”。例如：He fashioned the clay into a jar．他用黏土做成一个陶土罐子。B项modify意为“更改，修改”；C 项influence意为“影响，改变”；D项affect意为“影响，使感动”。显然，B、C、D三项不符合题意。

单选题 A. may B. should C. must D. can

单选题 A. by B. out of C. from D. through

单选题 A. prove B. make C. turn D. create

单选题 A. otherwise B. still C. yet D. even

单选题 A. assumed B. adopted C. believed D. surmised

【正确答案】 A

【答案解析】[解析] asstme意为“假定，设想”，多用于未证实的假定，根据题意，“早期的科学家，假定非人类动物的社会生活几乎完全是天生的，或是由遗传决定的”，所以A项为正确答案。B项adopt意为“采用，接受”；C项believe意为“相信”；D项surmise意为 “猜测，推测”，相当于“guess”。例如：She surrrtised as such．她如此猜测。

单选题 A. considerate B. considered C. considerable D. considering

单选题 A. statues B. statuses C. statutes D. statures

单选题 A. What's more B. Hence C. But D. However

【正确答案】 D

【答案解析】[解析] A项What's more表示递进；B项Hence意为“因此，所以”，表示因果关系。文中上一段提到“学习是动物的社会生活的一部分”，第二段接着讲“学习发生在动物小时候的印象中期”，两段间不存在递进或因果关系。But在表转折时一般不与句子分开，所以D项However为正确答案。

单选题 A. not B. only C. but D. solely

单选题 A. clarifies B. classifies C. defines D. outlines

【正确答案】 A

【答案解析】[解析] A项clarfies意为“使清楚，阐明”，例如：The government has time and again clarifled its position on equal pay for women．政府已经反复阐明政府对男女同工同酬的立场。B项classifies意为“分类，使……成为机密”；C项defines意为“下定义，界定”；D项outlines意为“画轮廓，作大纲”。根据原文的意思“一个例证很好地阐明了 ‘印象’的本质”，A项clarifies为最佳答案。