65. Although mockingbirds superbly mimic the songs and calls of many birds, they can nonetheless be quickly identified as mockingbirds by certain aural clues. 盡管模仿鳥學很多種鳥的鳴叫聲惟妙惟肖，但人類還是能夠依其聲音上的線索很快識別它們。

　　66. Not only can walking fish live out of water, but they can also travel short distances over land. 鲇魚不僅可以離開水存活，還可以在岸上短距離移動。

　　67. Scientists do not know why dinosaurs became extinct, but some theories postulate that changers in geography, climate, and sea levels were responsible. 科學家不知道恐龍為何絕種了，但是一些理論推斷是地理，氣候和海平面的變化造成的。

　　68. The science of horticulture, in which the primary concerns are maximum yield and superior quality, utilizes inFORMation derived from other sciences. 主要目的在于豐富和優(yōu)質的農藝學利用了其他科學的知識。

　　69. Snow aids farmers by keeping heart in the lower ground levels, thereby saving the seeds from freezing. 雪對農民是一種幫助，因為它保持地層土壤的溫度，使種子不致凍死。

　　70. Even though the precise qualities of hero in literary words may vary over time, the basic exemplary function of the hero seems to remain constant.

　　歷代文學作品中的英雄本色雖各有千秋，但其昭世功力卻是恒古不變的。

　　71. People in prehistoric times created paints by grinding materials such as plants and clay into power and then adding water. 史前的人們制造顏料是將植物和泥土等原料磨成粉末，然后加水。

　　72. Often very annoying weeds, goldenrods crowd out less hardy plants and act as hosts to many insect pests. 黃菊花通常令人生厭，它擠走不那么頑強的植物，并找來很多害蟲。

　　73. Starting around 7000 B.C., and for the next four thousand years, much of the Northern Hemisphere experienced temperatures warmer than at present. 大約從公元前七千年開始，在四千年當中，北半球的溫度比現(xiàn)在高。

　　74. When Henry Ford first sought financial backing for making cars, the very notion of farmers and clerks owning automobiles was considered ridiculous. 當亨利.福特最初制造汽車為尋求資金支持時，農民和一般職員也能擁有汽車的想法被認為是可笑的。

　　75. Though once quite large, the population of the bald eagle across North America has drastically declined in the past forty years. 北美禿頭鷹的數(shù)量一度很多，但在近四十年中全北美的禿頭鷹數(shù)量急劇下降。

　　76. The beaver chews down trees to get food and material with which to build its home. 水獺啃倒樹木，以便取食物并獲得造窩的材料。

　　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. 長卷毛狗曾被用作獵鴨時叼回獵物的獵犬，但是美國Kennel Club卻不承認它們?yōu)楂C犬，因為它們現(xiàn)在大多數(shù)作為寵物飼養(yǎng)。

　　78. As a result of what is now know in physics and chemistry, scientists have been able to make important discoveries in biology and medicine. 物理學和化學的一個成果是使得科學家們能在生物學和醫(yī)學上獲得重大發(fā)現(xiàn)。