It is often a challenge to keep a model completely "clean". By this, I mean a true representation of "the real world".

保证一个模型完全的“清洁”是有点难度，在此，我指的是真实世界的真实再现。

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That is especially true when it comes to clean energy, energy security, environmental stability, and climate change.

当我们在处理清洁能源、能源安全、环境稳定和气候变化等问题时尤其是这样。

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"If this is true, Lithuania has to clean up, accept responsibility, apologise, and promise that it will never happen again," she said.

“如果是真的，立陶宛将必须进行清理、承担责任、做出道歉并承诺再也不会发生这种事，”她说。

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The same is true when it comes to clean energy.

WHITEHOUSE: President Obama Talks Jobs in Allentown

And I think one of things we have to do is to clean up politics and to make it once again the situation that people can believe what they hear because I think the true disaster of this election was the non-vote and the number of people who said to me in the course of the campaign, but we can't believe anybody anymore.

BBC: News Online