有时候说“不”是必要的。

Sometimes it is necessary to say no.

《柯林斯英汉双解大词典》

此外，当你快要满足毕业要求的时候，有必要去申请毕业。

In addition, it is necessary to apply for graduation when you near the time that you will be completing your graduation requirements.

youdao

此外，在你即将完成毕业要求的时候，有必要去申请毕业。

In addition, it is necessary to apply for graduation when you're near the time that you will be completing your graduation requirements.

youdao

The point I wanted to make is that for every node, except the leaves, the leaves are the bottom of a tree in this case, are weird, right, they draw trees where the root is at the top, and the leaves are at the bottom.

你没必要看到整棵树，我想说的重点是,对每个节点来说，除了叶子节点,叶子节点指的是树的最下面的节点，电脑科学家都很奇怪,他们画树的时候根是在最上面的。

麻省理工公开课 - 计算机科学及编程导论课程节选

But sometimes it's necessary when you have really big course load

但是有时候课程量很大的时候这是必要的，

开放式的课程？ - SpeakingMax英语口语达人

Well, you don't have to just take what you've been handed round in life, functions like print F or round or maybe other functions you've seen in super sections or by poking around.

好的，你没必要把传给你的参数保存起来,像函数printf或者,或者你们看到的其他的函数,在超级课程中或闲逛的时候。

哈佛公开课 - 计算机科学课程节选