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来源:雅诚德英语网
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。
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。