c.问end of Cambrian Period的时候，以下哪个是对的？某选项说shallow and wide, but annious(单词不认识。。硬伤)
d.还有个问题忘了，某选项记得提到mud的变化
e刚check的时候发现：JJ里的那篇英文考古有几段就是考试里的！我摘出来了！
For decades, the Canadian geologist Martin Gibling has been intrigued by the tough-to-prove hypothesis that land plants created the shape of modern rivers hundreds of millions of years ago.
Plant roots reinforced the ground, the thinking goes, creating stable banks that funneled what once were wide, shallow water flows into narrower and deeper channels. By extension, that set the stage for lots of significant Earth history events, including the rise of human civilizations in modern river basins so many millennia later.
Now Gibling and postdoctoral scientist Neil Davies, both at Dalhousie University , have strengthened this case. When the pair compared a much-improved plant fossil record with evidence of how rivers changed very long ago, the transitions matched up. Back in the Cambrian period, which ended some 500 million years ago, the geologic record indicates that rivers were very shallow but wide things, almost floods that allowed rainwater to wash from largely barren solid ground to sea. Deposits left behind were preserved as sheets of coarse grains, some of which suggest these rivers were 1,000 or more times as wide as they were deep.
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发表于 2013-2-21 22:38:10
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楼主
谢谢