我们来看下面一段文字：
The floor of a river valley develops in one of two ways: as a rock-floored valley bottom or as an accumulation valley floor. A rock-floored valley is formed by a stream that no longer incises by cutting downward but rather erodes laterally in a course that winds from side to side across the valley floor. In a rock-floored valley, the valley slopes are undercut and steeped by the sideways erosion. The floor of the river channel lies in the bedrock, and on either side of the channel it is covered by only a thin layer of gravel and sand. As the stream swings across the valley floor, it deposits material on the insides of the bends in the channel.
通过对上面文字各个句子中的谓语动词的重点标示，读者应该会发现，文章的理解难度大大降低了，我们也不再用去无聊地思考为什么风能从一边到另一边地吹过峡谷底部了(winds from side to side across the valley floor)，因为我们知道重要的是思考rock-floored valley是怎么形成的(formed)，它怎么变陡峭的(undercut and steeped)，它所在的位置在哪里，被什么东西覆盖(lies and covered)，以及它沉淀物质在什么地方(deposits)。
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