据说煤中掺有石子和其它杂质须去掉时，至今仍得把煤在矿上筛过。

To this day coal is said to be screened in the colliery when it has stone and other impurities removed from it.

youdao

据说煤中掺有石子和其它杂质须去掉时，至今仍得把煤在矿上筛过。

To this day coal is said to be screened in the colliery when it has stone and other impurities removed from it.

youdao