The white-jacketed waitstaff are there when you need them.

当你需要穿白马甲的服务员时，他们就在那儿。

《柯林斯英汉双解大词典》

You can preset the radiators to come on when you need them to.

你可以预先调好暖气，使它在你需要的时候启动。

《牛津词典》

They always seem to slip away right when you need them most.

他们似乎经常就在你最需要的时候溜走了。

youdao

You will listen to them when they have a problem they need to talk about.

VOA: special.2009.09.13

Google's infrastructure will ensure that our tools are always ready, right when you need them.

ENGADGET: Google quietly snaps up internet security firm VirusTotal for an undisclosed amount

And what if that one manufacturer can't get you the parts when you need them?

BBC: New York taxi officials seek a new 'green' yellow cab

And perhaps even more importantly, will they be there when you need them?

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