It has been found that certain bats emit squeaks and by receiving the echoes, they can locate and steer clear of obstacles------or locate flying insects on which they feed. This echo-location in bats is often compared with radar, the principle of which is similar.

In group to remain in existence, a profit-making organization must, in the long run, produce something consumers consider useful or desirable.

81. 电视，这项从迅速变化和成长为标志的最普及和最有影响力的现代技术，正在步入一个新时代，一个极为成熟和多样化的时代，这将重塑我们的生活和世界。
Television the most pervasive and persuasive of modern technologies, marked by rapid change and growth, is moving into a new era, an era of extraordinary sophistication and versatility, which promises to reshape our lives and our world.

52. 无政府主义这个词描述的是一堆理论和态度，它们的主要共同点在于相信政府是有害的，没有必要的。
Anarchism is a term describing a cluster of doctrines and attitudes whose principal uniting feature is the belief that government is both harmful and unnecessary.

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59. 谨慎的航海员在出航前，会研究航向，记录的灯塔的位置，以便对各种可能出现的情况做到有备无患。
Before staring on a sea voyage, prudent navigators learn the sea charts, study the sailing directions, and memorize lighthouse locations to prepare themselves for any conditions they might encounter.

13. 理论在本质上是对认识了的现实的一种抽象和符号化的表达。
Essentially, a theory is an abstract, symbolic representation of what is conceived to be reality.

32. 科学家曾相信：氙气是不能形成化合物的。
That xenon could not FORM chemical compounds was once believed by scientists.

37. Lucretia Mott's的影响巨大，所以一些权威部门认定她为美国女权运动的创始人。
Lucretia Mott's influence was so significant that she has been credited by some authorities as the originator of feminism in the United States.

89. 由于空间不足，艺术博物馆在考虑购买和接受捐赠的艺术品时越来越慎重，有些情况下放弃其进一步改善收藏的机会。
Because of the space crunch, the Art Museum has become increasingly cautious in considering acquisitions and donations of art, in some cases passing up opportunities to strengthen is collections.

64. 电脑储存和由于电子微处理机得以实现的电控运用成倍的增加了现代打字机的功能。
The application of electronic controls made possible by the microprocessor and computer storage have multiplied the uses of the modern typewriter.

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38. 国际市场研究者的活动范围常常较国内市场研究者广阔。
The activities of the international marketing researcher are frequently much broader than those of the domestic marketer.

32. 科学家曾相信：氙气是不能形成化合物的。
That xenon could not FORM chemical compounds was once believed by scientists.

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24. 大多数物质遇冷收缩，所以他们的密度在固态时高于液态。
Most substance contract when they freeze so that the density of a substance's solid is higher than the density of its liquid.

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97. 每次我听说体育运动能够在国家间建立起友好感情，说世界各地的普通人只要能在足球场或板球场上相遇就会没有兴趣在战场上相遇的话，我都倍感诧异。
I am always amazed when I hear people saying that sport creates goodwill between the nations, and that if only the common peoples of the world could meet one another at football or cricket, they would have no inclination to meet on the battlefield.