We may drop one of the recitations, just depending on course size, all right?

我们可能会取消一个复习课，取决于课程大小，可以么？

麻省理工公开课 - 计算机科学及编程导论课程节选

So that explains why they're so reactive, they're all very willing to give up that one s orbital and then drop to a lower energy level.

这就解释了它们的化学性质为什么非常活泼，它们都很愿意失去那个，s，电子,然后降到更低的能级上去。

麻省理工公开课 - 化学原理课程节选