Now, as obvious a statement as that is in this algorithm, it turns out that is the key to this whole problem being solved correctly without my algorithm looping infinitely.

这是此算法中很明显的一句话，也是正确解决,整个问题的关键,否则此算法就会陷入死循环。

哈佛公开课 - 计算机科学课程节选

In a help session what he might do typically is solve between four and eight problems that illustrate the key principle being talked that week.

在帮助课程中他一般会,解决4到8个问题,来阐明那一周教的关键原理。

麻省理工公开课 - 媒体、教育、市场课程节选

The point is the arrow A, somebody has chosen to write in terms of i prime and j prime as Ax prime and Ay prime.

解决问题的关键在于矢量 A,可以用这样的形式来描述,i' ? Ax' + j' ? Ay'

耶鲁公开课 - 基础物理课程节选