jì / zhě / jué / dìng / xún / gēn / jiū / dǐ / chá / qīng / shì / gù / fā / shēng / de / zhēn / zhèng / yuán / yīn

记者决定寻根究底，查清事故发生的真正原因。

The reporter decided to get to the bottom of things and find the true cause of the accident.