A long time ago all horses lived in wild herds on the broad grassy plains of Asia.

很久很久以前, 所有的马都成群地生活在广阔的亚洲草原上。

The grassy plain gave way to an extensive swamp.

【plain】青草覆盖的平原被广阔的沼泽地所取代。

They followed great groups of the animals across the grassy plains. At that time, there were millions of these animals in the American west.

他们跟着一大群动物穿过长满青草的平原。当时，在美国西部有数百万只这样的动物。

They think of the Internet as a wide open, grassy plain and they can watch to see what users do and where they go.

他们认为 Internet 是一片开阔的草地，他们可以观察用户的行为和去向。

And in 2011, paleontologsts from China studied the tooth enamel of Gigantopithecus and found that it fed exclusively on C3 plants -- the ones that tend to grow in cool, humid forests rather than warm, grassy plains.

2011 年， 中国古生物学家研究了 Gigantopithecus 的牙釉质， 发现它只以 C3 植物为食——这些植物往往生长在凉爽潮湿的森林中，而不是温暖的草地平原。