84.他的教书生涯始于麻省理工学院，但是William Rainey Harper把他吸引到了新成立的芝加哥大学。他在那里正式任职长达整整一代人的时间。他的高级作文课上的学生觉得他在课上古板得可怕，但私下交流却富有同情和理解。
85. The sloth pays such little attention to its personal hygiene that green algae grow on its coarse hair and communities 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.
85.树獭即不讲究卫生，以至于它粗糙的毛发上生出绿苔，成群的寄生蛾生长在它的皮毛深处，变成毛毛虫，并以它的脏毛为食。她的肌肉不能让他哪怕在很短的距离以内以每小时一公里的速度移动。它能做的最敏捷的动作就是挥一挥它弯曲的胳膊。
86. Artificial flowers are used for scientific as well as for decorative purposes. They are made from a variety of materials, such as way and glass, so skillfully that they can scarcely be distinguished from natural flowers.
86.人造花卉即可用于科学目的，也可用于装饰目的，它们可以用各种各样的材料制成，臂如蜡和玻璃；其制作如此精巧，几乎可以以假乱真。
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 coal-rich regions of the United States.
87.在伊利诺州Angonne市的一个废弃煤矿的三年研究取得了成果，科学家们相信这些成果可以帮助改造把美国产煤区弄得伤痕累累的数千个旧煤场。
88. When the persuading and the planning for the western railroads had finally been completed, the really challenging task remained: the dangerous, sweaty, backbreaking, brawling business of actually building the lines.
88.当有关西部铁路的说服和规划工作终于完成后，真正艰难的任务还没有开始；即危险，吃力，需要伤筋动骨和吵吵嚷嚷的建造这些铁路的实际工作。
89. 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.
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是越来越慎重，有些情况下放弃其进一步改善收藏的机会。
90. The United States Constitution requires that President be a natural-born citizen, thirty-five years of age or older, who has lived in the United States for a minimum of fourteen years.
90.美国宪法要求总统是生于美国本土的公民，三十五岁以上，并且在美国居住了至少十四年。
91. Arid regions in the southwestern United States have become increasingly inviting playgrounds for the growing number of recreation seekers who own vehicles such as motorcycles or powered trail bikes and indulge in hill-climbing contests or in caving new trails in the desert.
91.美国西部的不毛之地正成为玩耍的地方，对越来越多拥有摩托车或越野单车类车辆的，喜欢放纵于爬坡比赛或开辟新的沙漠通道的寻欢作乐者具有不断增长的吸引力。
92. Stone does decay, and so tools of long ago have remained when even the bones of the man who made them have disappeared without trace. liuxuepaper.com