尽管非洲是是世界上第二个最大的大陆，整个地区是欧洲的三倍，但撒哈拉大沙漠以南的海岸线却只相当于欧洲的五分之一长，而且没有那么多的天然良港。
Although Africa is the world's second-largest continent, with an area three times that of Europe, its coastline south of the Sahara is about a fifth as long and lacks many good natural harbors.
这些有孔虫大约有200至350微米大，或者一毫米的五分之一到三分之一长。
These foraminifera were roughly 200 to 350 microns large, or a fifth to a third of a millimeter long.
这些有孔虫大约有200至350微米大，或者一毫米的五分之一到三分之一长。
These foraminifera were roughly 200 to 350 microns large, or a fifth to a third of a millimeter long.
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