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  3. Several hundred million years ago, plants similar to modern ferns covered vast stretches of the land. Some were as large as tree

Several hundred million years ago, plants similar to modern ferns covered vast stretches of the land. Some were as large as tree

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问题     Several hundred million years ago, plants similar to modern ferns covered vast stretches of the land. Some were as large as trees, with giant fronds bunched at the top of trunks as straight as pillars. Others were the size of bushes and formed thickets of me undergrowth. Still others lived in the shade of giant club mosses and horsetails along the edges of swampy lagoons where giant amphibians swam.
    A great number of these plants were true ferns, reproducing themselves without fruits or seeds. Others had only the appearance of ferns. Their leaves had organs of sexual reproduction and produced seeds. Although their "flowers" did not have corollas these false ferns(today completely extinct)ushered in the era of flowering plants. Traces of these floras of the earliest times have been preserved in the form of fossils. Such traces are most commonly found in shale and sandstone rocks wedged between coal beds.
    Today only tropical forests bear living proof of tile ancient greatness of ferns. The species that grow there are no longer those of the Carboniferous period, but their variety and vast numbers, and the great size of some, remind us of the time when ferns ruled the plant kingdom.
What does the passage mainly discuss?
选项 A、Plant reproduction.
B、An ancient form of plant life.
C、How to locate fossils.
D、Tropical plant life.
答案B
解析 主旨题。这篇文章主要讨论的就是远古时代的一种植物，故答案选D；A“植物繁殖”，如果以此为标题，文章说的就应该是植物是怎样繁殖的，那么说的植物就应该是很多种不同种类的植物是怎样繁殖的。
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