要把社区工作做好，协作活动是必不可少的。

Cooperative activity is essential to effective community work.

《牛津词典》

丰富多彩的、多样化的文化生活对于这对夫妇而言是必不可少的。

A rich and varied cultural life is essential for this couple.

《柯林斯英汉双解大词典》

氧气在细胞呼吸的新陈代谢过程中是必不可少的，它能使细胞有效地从有机食物中获取能量。

Oxygen is essential for the metabolic process known as cell respiration that allows cells to efficiently harvest energy from organic food.

youdao

First, the historical prologue that's so central to the suzerainty treaty, grounds the obligations of Israel to Yahweh in the history of his acts on her behalf.

第一点，历史开场白在领主契约中,是必不可少的，规定了犹太人,对上帝需要履行的义务。

耶鲁公开课 - 旧约导论课程节选

And as far as right now, just study hard, learn the material that will help you succeed.

就现阶段来讲，最重要的是勤奋学习，有一些知识是走向成功必不可少的，你要好好学习这些知识。

如果是在考虑留学 - SpeakingMax英语口语达人

We're going to get a deep insight if it's a necessary truth about death that everyone dies alone.

如果这是对死亡来说必不可少的真理,那我们能得到一些深刻理解。

耶鲁公开课 - 死亡课程节选