71. People in prehistoric times created paints by grinding materials such as plants and clay into power and then adding water.
71.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.
72.黃色菊花通常令人生厭，它擠走不那么頑強(qiáng)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.
73.大約從公元前七千年開始，在四千年當(dāng)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.
74.當(dāng)亨利.福特最初制造汽車為尋求資金支持時(shí)，農(nóng)民和一般職員也能擁有汽車的想法被認(rèn)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.
75.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。
71.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.
72.黃色菊花通常令人生厭，它擠走不那么頑強(qiáng)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.
73.大約從公元前七千年開始，在四千年當(dāng)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.
74.當(dāng)亨利.福特最初制造汽車為尋求資金支持時(shí)，農(nóng)民和一般職員也能擁有汽車的想法被認(rèn)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.
75.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。