词典释义：
双语例句
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The leaves of ferns, reeds, and other plants, are frequently found between layers of shale or slaty clay, beautifully perfect, but converted into coal.
我们通常能在页岩层和黏板岩层中发现蕨类植物，芦苇和其它植物的叶子，但是这些叶子都完全转变为了煤。