When we have just a single bond in them molecule, you have all the freerotation you want, you can just spin it around, there's nothing keeping it in place.
当我们在分子力只有一个单键时，你可以随意旋转，你可以让它转起来，没有什么东西能固定住它。
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Look at the siege and lunch only and rotation-free, she tired, sitting in a corner to rest.