必须的

Although nitrogen is nontoxic and largely inert, it can act as a simple asphyxiant by displacing the oxygen in air to levels below that required to support life.

尽管氮无毒且很大程度上不活泼，通过取代空气中的氧，使之下降到维持生命所必须的水平以下它可以为简单的窒息物。

Although nitrogen is nontoxic and largely inert, it can act as a simple asphyxiant by displacing the oxygen in air to levels below that requiredto support life.

尽管氮无毒且很大程度上不活泼，通过取代空气中的氧，使之下降到维持生命所必须的水平以下它可以为简单的窒息物。

B-Complex vitamins help convert food into energy and are necessary for normal functioning of the nervous system.

维生素B族，能够帮助将事物转化为能量，及对正常的神经系统的功能是必须的。

In this interpretation IP is a subset of IR; this will be typical of RDF semantic interpretations

一般来说IP是IR的子集，因为属性也可以当成资源，作为三元组的主体或客体，都这并不是必须的。

Such belt-tightening had proved necessary even in the months before the rescue.

这样的收紧裤腰带过日子即便在救助后的几个月也被证明是必须的。

Everybody's life aren't Bon voyage, situation and frustrate is you have to of friend.

13-6、每个人的生活都不是一帆风顺的，遭遇和挫折是你必须的朋友。

Wal-Mart is selling organic food, and even Coca-Cola is launching a wellness drink.相关的例句It is easy to see how even a family which had had as good food as it wished and a few extras could be down to bread and scrape the barrel inside a month if the "demon drink" took hold.

即使是一个本来想吃得好些就能吃得好些、尚有盈余可供某些别的开支的家庭，倘若嗜上酒来，则在不到一个月的时间里，就可以穷落下来，以致只能吃面包及必须掏尽家底，不难明白这种现象究竟是怎么回事。

If the packet destination address is not in the bridge table, the packet is flooded on all forwarding interfaces in the bridge group.

对于可路由的接口和交换虚接口，IP地址的分配不是必须的。

Here, however, a brief editorial cadenza is inserted for the use of students which, although not a requirement, may be played in the exam.

在这里，只是插入一个简短的编辑过的华彩供学生使用，不是必须的，也许只是考试时弹奏。

CRP/CAP Catabolite activator protein,CAP is an activator required for high level transcription of the lac operon.The active molecule is a CRP dimer that binds 3'5' cyclic AMP to form a CRP-cAMP complex.

CRP/CAP 分解代谢物激活蛋白CAP是Lac操纵子高水平转录的一个必须的激活因子，有活性的CRP二聚体与3ˊ5ˊ-环式AMP结合形成CRP-cAMP复合物。

Do you know, i need you to come back

你知道吗，我需要你回来

Yang yinshu、Wang xiangsheng、Li decang,The first discovery of haemaphysalis conicinna.

1〕 杨银书，王祥生，李德昌。安徽省首次发现嗜群血蜱。