句中“the nuclear explosions was occurred 不用被动语态 ”的原因?另外如何改正?

题目

句中“the nuclear explosions was occurred 不用被动语态 ”的原因?另外如何改正?
This point is best illustrated with the example of Hiroshima and Nagasaki in Japan,the nuclear explosions was occurred （不用被动语态） nearly a half century later,the residual nuclear radiation badly has been endangered the natural ecosystems in the native.
核弹不启动怎么会自己爆炸，要是自己就能爆炸岂不是太恐怖了，所以我觉得是用被动合适，可批改就说应该是主动，到底是怎么算正确啊？

答案