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题目材料：
Why does so much of our coal and petroleum date from the Carboniferous period? The orthodox view is that Carboniferous swamps provided optimal conditions for fossil fuel formation. After the Carboniferous, the world became drier, and conditions became less favorable. But is that all there is to it? Forests didn't disappear after the Carboniferous. If anything, there were even more trees, growing ever more widely at higher elevations, and growing to greater heights over the Mesozoic and Cenozoic. After the Carboniferous, the continents may have been drier inland, but they still had lots of streams, rivers, and coastal wetlands. Trees from dry highlands could easily have washed into rivers and accumulated in lowland marshes. Something other than a change in climate must have occurred.
以上解析由 考满分老师提供。
