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  3. How to Get Preserved as a Fossil 【71】Unfortunately the chances of any animal become a fossil are not very great, and【72】the

How to Get Preserved as a Fossil 【71】Unfortunately the chances of any animal become a fossil are not very great, and【72】the

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问题                   How to Get Preserved as a Fossil
    【71】Unfortunately the chances of any animal become a fossil are not very great, and【72】the chances of a fossil then being discovered many thousand of years later are even less.【73】It is not surprising that all the millions of animals that have lived in the past【74】we actually have fossils of only very few.
   【75】There are several ways into which, animals and plants may become fossilized.【76】First, it is essential that the remains are buried, as though dead animals and plants are quickly destroyed【77】if they remain exposed the air. Plants rot, while insects and hyenas eat the flesh and bones of animals. 【78】Finally, the few remaining bones soon disintegrate the hot sun and pouring rain. If buried in suitable conditions, however, animal and plant remains will be preserved. 【79】The same chemicals change sand and silt into hard rock will aim enter the animal and plant remains and make them hard too.【80】When this happens, we say that they become fossilized.
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答案chemicals change改成chemicals that change
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