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. 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. 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. 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. 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. 石头不会腐烂，所以以前的(石器)工具能保存下来，虽然它们的制造者已经消失的无影无踪。

93. Insects would make it impossible for us to live in the world; they would devour all our crops and kill our flocks and herds, if it were not for the protection we get from insect-eating animals. 昆虫就将会使我们无法在这个世界上居住;如果我们没有受到以昆虫为食的动物的保护，昆虫就会吞嚼掉我们所有的庄稼并杀死我们饲养的禽兽。

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. 确实，他们在探险中遇到了极具威胁性的困难和危险，而他们的装备会让一个现代登山者想一想都会浑身颤栗。不过他们并不是刻意去追求刺激的。

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. 老人和年轻人之间只有一个区别：年轻人的前面有辉煌的未来，老年人灿烂的未来却已在它们身后。这也许就是困难之所在。

96. I find young people exciting. They have an air of freedom, and they have not a dreary commitment to mean ambitions or love comfort. They are not anxious social climbers, and they have no devotion to material things. 我们位年强人振奋。它们带有自由的气息，他们不会为狭隘的野心和贪婪享受而孜孜以求。他们不是焦虑的向上爬的人，他们不会对物质性的东西难舍难分。

97. 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. 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。

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 combative instincts are around. 没有可能仅仅为了娱乐或锻炼而运动：一旦有了问题，一旦你觉得你输了你和你所属团体会有失体面时，你最野蛮的好斗本能就会被激发出来。

99. 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. 人们已经发现，某些蝙蝠发出尖叫声并靠接受回响来锁定和避免障碍物——或者找到它们赖以为生的昆虫。蝙蝠这种回响定位法常拿来和原理与之很相近似的雷达相比。

100. As the time and cost of making a clip drop to a few days and a few hundred dollars, engineers may soon be free to let their imaginations soar without being penalized by expensive failure. 随着芯片制造时间和费用降低到了几天和几百美元，工程师们可能很快可以任他们的想象驰骋而不会被昂贵的失败所惩罚。