That accord mandated by the U.S.Congress is a necessary prerequisite for American aerospace firms to bid on a pending Indian purchase of 126 multi-role fighter jets, potentially the largest-ever arms sale.

VOA: standard.2009.07.20

Purity, which is the absence of impurity, is a prerequisite for access to the holy or for holy status.

纯洁，不纯的反义词，是接近神圣或达到神圣状态的先决条件。

耶鲁公开课 - 旧约导论课程节选