火花引发了一场巨大的爆炸。

The spark ___set ___off a massive explosion.

公告引发了一波骚乱。

The announcement ___set ___off a wave of riots.

他会通过点燃一些火柴来触发烟雾报警器。

He would ___set ___off the smoke alarm by lighting some of his matches.