65. although mockingbirds superbly mimic the songs and calls of many birds, they can nonetheless be quickly identified as mockingbirds by certain aural clues. 尽管模仿鸟学很多种鸟的鸣叫声惟妙惟肖，但人类还是能够依其声音上的线索很快识 尽管模仿鸟学很多种鸟的鸣叫声惟妙惟肖，但人类还是能够依其声音上的线索很快识 别它们。 别它们。 66. not only can walking fish live out of water, but they can also travel short distances over land. 12 鲇鱼不仅可以离开水存活，还可以在岸上短距离移动。 鲇鱼不仅可以离开水存活，还可以在岸上短距离移动。 67. scientists do not know why dinosaurs became extinct, but some theories postulate that changers in geography, climate, and sea levels were responsible. 科学家不知道恐龙为何绝种了，但是一些理论推断是地理， 科学家不知道恐龙为何绝种了，但是一些理论推断是地理，气候和海平面的变化造成 的。 68. the science of horticulture, in which the primary concerns are maximum yield and superior quality, utilizes information derived from other sciences. 主要目的在于丰富和优质的农艺学利用了其他科学的知识。 主要目的在于丰富和优质的农艺学利用了其他科学的知识。 他科学的知识 69. snow aids farmers by keeping heart in the lower ground levels, thereby saving the seeds from freezing. 雪对农民是一种帮助，因为它保持地层土壤的温度，使种子不致冻死。 雪对农民是一种帮助，因为它保持地层土壤的温度，使种子不致冻死。 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. 历代文学作品中的英雄本色虽各有千秋，但其昭世功力却是恒古不变的。 历代文学作品中的英雄本色虽各有千秋，但其昭世功力却是恒古不变的。 71. people in prehistoric times created paints by grinding materials such as plants and clay into power and then adding water. 史前的人们制造颜料是将植物和泥土等原料磨成粉末，然后加水。 史前的人们制造颜料是将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. 黄菊花通常令人生厌，它挤走不那么顽强的植物，并找来很多害虫。 黄菊花通常令人生厌，它挤走不那么顽强的植物，并找来很多害虫。 73. starting around 7000 b.c., and for the next four thousand years, much of the northern hemisphere experienced temperatures warmer than at present. 大约从公元前七千年开始，在四千年当中，北半球的温度比现在高。 大约从公元前七千年开始，在四千年当中，北半球的温度比现在高。