This huge quantity would be enough to easily fulfill the requirements of everyone on the planet if the water arrived where and when people needed it.

如果雨水逢时逢地的降落在人们需要的地方，这一巨大数目将足够轻易地满足地球上每一个人的需求。

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It pays to know in advance what files to look for, where they are, and to ensure that they are indeed generated properly and will be available when needed.

它需要提前知道要寻找哪些文件、它们位于何处，并要确保确实正确地生成了它们，并且在需要的时候它们将是可用的。

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Capture all your thoughts on paper (or digitally) - don't let them float around in your head, where they will surface at inappropriate times, stress you out and be forgotten when they are needed.

将你所有的想法都记录在纸上(或者是电子记事本中)——不要让他们在你的脑中漂浮，在不适当的时候出现在你的脑中，使你感到紧张，但是当你需要他们的时候你又忘记了。

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It requires not 10 aircraft carrier battle groups but, to do it right and when and where needed, 20.

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Moreover, the electric industry has a proven track record of adding additional generating capacity and transmission solutions when and where needed and of coordinating effectively to address reliability concerns.

WHITEHOUSE: Energy and Environment Latest News | The White House

And we need a system that is flexible to changing economic demands, attracting workers when and where they are needed and easing immigration when demand for workers slows.

CNN: U.S. needs 21st century immigration plan