史蒂文森博士正在分析一种元素——活树和死树年轮中的碳-14。

Doctors Stevenson is analyzing one element—carbon-14 in ring from both living and dead trees.

youdao

史蒂文森博士正在分析一种元素——活树和死树年轮中的碳-14。

Doctors Stevenson is analyzing one element—carbon-14 in ring from both living and dead trees.

youdao