调查人员正在研究导致那次事故发生的一系列事件。

Investigators are studying the sequence of events that ___led ___up ___to the accident.

历史学家们争论是哪些因素导致了罗马帝国的衰亡。

Historians debate which factors ___led ___up ___to the fall of the Roman Empire.

在宣布之前的几周里，激烈的争论暗示着一场重大的政策转变即将到来。

The heated arguments in the weeks ___leading ___up ___to the announcement suggested a major policy shift was coming.