Because step five is that we need to fill in our bonding electrons, and we start it with filling in two electrons per bond.

因为第五步要做的是将我们的成键电子填在这，所以我们开始在每个键处填上两个电子。

麻省理工公开课 - 化学原理课程节选

Let's take a step back and ask are all kinds of cells really the same and start by talking about two cells that I know you know are quite different.

让我们退一步并问一句,所有细胞真的都是一样的么,我们不妨从两种,看起来截然不同的细胞谈起

耶鲁公开课 - 生物医学工程探索课程节选

So, we start on C and then we go up to D-- a whole step.

我们从C开始,然后上升到D,一个全音级

耶鲁公开课 - 聆听音乐课程节选

Now you start a process, a cyclic process, where the first step in the process is denaturing the DNA.

然后你就可以开始一个循环步骤,第一步是使DNA变性

耶鲁公开课 - 生物医学工程探索课程节选