If you put a ball on the floor, it will roll to one side of the house.

假如你在地板上放一颗球，球就会滚到房子的另一边。

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Begin to roll the leaf from one side.

然后从一边往另一边卷起叶子。

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Begin to roll the leaf from one side.

然后从一边往另一边卷起叶子。

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