英语语法分析

Helium is the by product of millennia of radioactive decay from the elements thorium and uranium.

氦是钍和铀元素数千年放射性衰变的副产品。

For millennia the average person's stance toward providing for himself had been, ultimately I'm on my own.

几千年来，一般人对于养活自己的立场是，最终我要靠自己。

Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form.

一旦土壤被侵蚀，新的土壤只有经过几个世纪或几千年才能形成。