【正文】 12。蝙蝠這種回響定位法常拿來和原理與之很相近似的雷達(dá)相比。98. It is impossible to say simply for the fun and exercise: as soon as the question of prestige arises, as soon as you feel that you and some larger unit will be disgraced if you lose, the most savage bative instincts are around.：一旦有了問題，一旦你覺得你輸了你和你所屬團(tuán)體會有失體面時，你最野蠻的好斗本能就會被激發(fā)出來。他們不是焦慮的向上爬的人，他們不會對物質(zhì)性的東西難舍難分。96. I find young people exciting. They have an air of freedom, and they have not a dreary mitment to mean ambitions or love fort. They are not anxious social climbers, and they have no devotion to material things.。95. There is only one difference between an old man and a young one: the young man has a glorious future before him and old one has a splendid future behind him: and maybe that is where the rub is.：年輕人的前面有輝煌的未來，老年人燦爛的未來卻已在它們身后。94. It is true that during their explorations they often faced difficulties and dangers of the most perilous nature, equipped in a manner which would make a modern climber shudder at the thought, but they did not go out of their way to court such excitement.，他們在探險中遇到了極具威脅性的困難和危險，而他們的裝備會讓一個現(xiàn)代登山者想一想都會渾身顫栗。93. Insects would make it impossible for us to live in the world。91. Arid regions in the southwestern United States have bee increasingly inviting playgrounds for the growing number of recreation seekers who own vehicles such as motorcycles or powered trail bikes and indulge in hillclimbing contests or in caving new trails in the desert.，對越來越多擁有摩托車或越野單車類車輛的，喜歡放縱于爬坡比賽或開辟新的沙漠通道的尋歡作樂者具有不斷增長的吸引力。89. Because of the space crunch, the Art Museum has bee increasingly cautious in considering acquisitions and donations of art, in some cases passing up opportunities to strengthen is collections.，藝術(shù)博物館在考慮購買和接受捐贈的藝術(shù)品是越來越慎重，有些情況下放棄其進(jìn)一步改善收藏的機(jī)會。87. Three years of research at an abandoned coal mine in Argonne, Illinois, have resulted in findings that scientists believe can help reclaim thousands of mine disposal sites that scar the coalrich regions of the United States.，科學(xué)家們相信這些成果可以幫助改造把美國產(chǎn)煤區(qū)弄得傷痕累累的數(shù)千個舊煤場。它能做的最敏捷的動作就是揮一揮它彎曲的胳膊。85. The sloth pays such little attention to its personal hygiene that green algae grow on its coarse hair and munities of a parasitic moth live in the depths of its coat producing caterpillars which graze on its mouldy hair. Its muscles are such that it is quits incapable of moving at a speed of over a kilometer an hour even over the shortest distances and the swiftest movement it can make is a sweep of its hooked arm.，以至于它粗糙的毛發(fā)上生出綠苔，成群的寄生蛾生長在它的皮毛深處，變成毛毛蟲，并以它的臟毛為食。他在那里正式任職長達(dá)整整一代人的時間。81. 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.，這項(xiàng)從迅速變化和成長為標(biāo)志的最普及和最有影響力的現(xiàn)代技術(shù)，正在步入一個新時代，一個極為成熟和多樣化的時代，這將重塑我們的生活和世界。79. The practice of making excellent films based on rather obscure novels has been going on so long in the United States as to constitute a tradition.，已經(jīng)成為傳統(tǒng)。77. Poodles were once used as retrievers in duck hunting, but the American Kennel Club does not consider them sporting dogs because they are now primarily kept as pets.，但是美國Kennel Club卻不承認(rèn)它們?yōu)楂C犬，因?yàn)樗鼈儸F(xiàn)在大多數(shù)作為寵物飼養(yǎng)。75. Though once quite large, the population of the bald eagle across North America has drastically declined in the past forty years.，但在近四十年中全北美的禿頭鷹數(shù)量急劇下降。73. Starting around 7000 ., and for the next four thousand years, much of the Northern Hemisphere experienced temperatures warmer than at present.，在四千年當(dāng)中，北半球的溫度比現(xiàn)在高。71. People in prehist