"And I said to him that those were two easy promises to make because those two things I could not change."

VOA: standard.2009.10.01

Often, for a particular state change, it is easy to calculate two of these, but not the third.

对于一些特定的状态变化，它们中的两个很好计算，但是第三个往往不容易计算。

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and it's not really easy to change that.

这一点不容易改变。

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