One, two, three, four, so on each level of the picture I'm drawing, I've seem only to be looking at each number once.

，2，3，4，可见，在我画的,这幅图的每一层上，对每个数字,都只会用到一次。

哈佛公开课 - 计算机科学课程节选

On each level in the picture, I'm touching each number once, alright.

在这幅图的每一层上，我只会移动每个数字一次。

哈佛公开课 - 计算机科学课程节选

There are hundreds,thousands of them known now, and each one has a specific character and one aspects of its character is that it only binds and cuts at a particular sequence of DNA.

已知的有成百上千种,每一种都有自己的特性,特性之一是,只结合和切割特定的某一种DNA序列

耶鲁公开课 - 生物医学工程探索课程节选