Yuán / gǔ / dài / shì / dì / qiú / lì / shǐ / shàng / fēi / cháng / màn / cháng / de / yí / gè / dì / zhì / shí / dài

元古代是地球历史上非常漫长的一个地质时代。

The Proterozoic was a very long geological era in Earth's history.