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TF阅读真题第837篇Changes in Native American Food Production
Changes in Native American Food Production Changes in Native American Food Production 1 Native Americans expanded their sources of food in the centuries around the end of the fir...
TF阅读真题第871篇Carbon Dioxide Levels in the Ocean
题目： Carbon Dioxide Levels in the Ocean The concentration of carbon dioxide gas (CO2) is rising in the atmosphere, and some of this CO2 is taken up by ocean surface waters. To ...
TF阅读真题第797篇The Australlan Megatauna Extinctions
The Australlan Megatauna Extinctions Many of the species of large animals(megafauna) such as mammoths, mastodons, ground sloths, and giant deer that roamed the Earth tens of thous...
