What exactly that purgation will entail and why Milton's voice needs to be purged at all I think these questions are really the subject of the entire rest of the poem.

这种净化是很有必要的,弥尔顿的语言为什么需要被完全净化,我认为这个问题才是所有剩余诗歌,真正的主题。

耶鲁公开课 - 弥尔顿课程节选

I mean, it's kind of a necessity for a lot of students, myself included, to have these jobs

我的意思是，对于大多数学生而言，
也包括我在内，做这些工作是很有必要的，

再没时间也要挤出来 - SpeakingMax英语口语达人

And these are kind of need in the kids.

这对于孩子们来说是很有必要的。

麻省理工公开课 - 媒体、教育、市场课程节选

You guys have also seen vectors, I'm pretty sure, but it is worth going over some properties and some may be new and some may be old.

我很肯定你们曾接触过矢量,但复习一下相关的性质是很有必要的,有些可能是新知识,有些是已经学过的

耶鲁公开课 - 基础物理课程节选

Because sometimes it's useful to think about the payoffs, as coming from "i's" own choice and everyone else's choices.

因为有时候考虑在i和对手,在不同选择下的收益是很有必要的

耶鲁公开课 - 博弈论课程节选