必须使这个问题成为焦点。

The issue must be brought into sharper focus.

《牛津词典》

首先我们必须找出问题所在。

First of all we must identify the problem areas.

《牛津词典》

我们必须设法解决交通污染问题。

We must address ourselves to the problem of traffic pollution.

《牛津词典》

Another part of the problem of learning language is you have to figure out what the boundaries are between the words.

学习语言的另一个问题是,你必须得确定单词之间的界线是什么

耶鲁公开课 - 心理学导论课程节选

If the question of time is not explicitly brought up, then you should know that you have to use this formula.

如果时间的问题并没有明确提出,那你应该知道,必须要用这个式子

耶鲁公开课 - 基础物理课程节选

The problem with that answer is before you say something is scripture, you have to say why is it scripture,for whom is it scripture, and what does that mean?

这个回答的问题在于,在把某样东西定义为圣典前，必须明确为什么，对谁来说是圣典，那是什么意思？

耶鲁公开课 - 新约课程节选