在植物把它们播撒四方之后，它们可以长期存留在湖底的淤泥里或者或化石中。
After plants spread theirs far and wide it can be preserved in lakebeds or fossilized in soil.
只有积极的研究发展项目才能够摆脱我们对化石燃料依赖，或找到解决这一问题的方法。
Only an aggressive research and development program might find ways of breaking our dependence on fossil fuels or dealing with it.
在这种情况下，骨骼或外壳的原始成分会保留下来，但化石会变得更坚硬、更耐用。
In such cases, the original composition of the bone or shell remains, but the fossil is made harder and more durable.
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