进军美利坚tpo阅读疑难解答帖

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sources of 是个词组。。。origin的意思
kila1002 发表于 2010-8-10 19:08

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TPO5 THE CAMBRIAN EXPLOSION(寒武纪大爆发)
Scientists have asked important questions about this explosion for more than a century. Why did it occur so late in the history of Earth? The origin of multi ...
weiyang1220 发表于 2010-8-11 00:20

Why did it occur so late in the history of Earth? The origin of multicellular forms of life seems a relatively simple step compared to the origin of life itself.这个过程看起来是个相对简单的步骤，但为什么发生这么晚呢？其实就是说它为什么用了这么长时间来完成这个过程。