生物系统亿万年来都在这样做。

Biological systems have been doing this for billions of years.

《柯林斯英汉双解大词典》

在繁荣的三月，该国已鼓励其亿万年轻人迁入城市。

In its march to prosperity, the country has encouraged hundreds of millions of its young people to move into cities.

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据我们所知，地球大气中20%左右的氧含量已保持了亿万年之久。

As far as we can tell Earth's atmospheric oxygen has remained at about 20 percent for hundreds of millions of years.

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