先进的筛查技术现在可以在极早期发现某些癌症的存在。

Advanced screening can now detect the ___occurrence of some cancers at very early stages.

图表清晰地显示了近几十年来两个主要经济高峰的出现。

The graph clearly shows the ___occurrence of two major economic peaks in recent decades.

研究人员正在研究极端天气事件增多的现象。

Researchers are studying the increased ___occurrence of extreme weather events.