But the report says the devices should be used only when necessary.

VOA: special.2010.05.25

Have we at least found something interesting,necessary, unique to death when we say,Nobody can die my death for me.

我们是否至少找到一些有趣，必要，独特的东西，当我们说“没有人能代替我死亡。

耶鲁公开课 - 死亡课程节选

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

These include lasers, noise makers and,when necessary, killing problem animals.

VOA: special.2009.04.01

When they thought it was necessary, they maintained peace by destroying communities and forcibly moving populations.

一旦他们觉得有必要，就会为了维护和平，毁灭其他群体,强制迁移人口。

耶鲁公开课 - 新约课程节选

Main said the government is now willing to go directly to court to shut down mines when necessary, and he called on Congress to enact tougher enforcement measures.

VOA: standard.2010.04.27

Because when we see that something is just necessary, we-- it reduces the sting of it.

因为当我们认识到有些事是必然的-,它便感少了我们对它的痛苦。

耶鲁公开课 - 死亡课程节选

Some cesareans are medically necessary. But in other cases, women just want the convenience of knowing when they will give birth.

VOA: standard.2010.06.30

In my experience, decisions moved with the process of risks, mitigation like malaises When the Taliban arrived in the village, it takes 96 hours for an army commander to obtain necessary approvals to act.

以我的经验来看，决定的执行是有一定的风险的,当塔利班分子进入到村子后，一个军队指挥官要花去96个小时来获得必要的批准才能行动。

普林斯顿公开课 - 国际座谈会课程节选

President Obama, who had set an early August deadline, now predicts necessary action in September when Congress returns from a month-long recess.

VOA: standard.2009.07.29

The president also says he will send the military into battle only when needed, and will give them the necessary training and equipment.

VOA: standard.2009.05.23

"That is why I will send our servicemen and women into harm's way only when it is necessary and ensure that they have the training and equipment they need when they enter the theater of war,".

VOA: standard.2009.05.23

Speaking via Skype,she says no. "I think further studies will be necessary to show whether the differences we've demonstrated depending on delivery mode of babies when they first emerge into the world actually carry over time, and whether those differences might contribute to health outcomes."

VOA: standard.2010.06.30

"It is a promise that as long as I am your Commander in Chief, I will only send you into harm's way when it is absolutely necessary, and with the strategy, the well-defined goals, the equipment and the support you need to get the job done,"

VOA: standard.2009.05.22