这一事件引发了一连串危险的事件，最终导致了一场重大危机。

The incident started a dangerous ___chain of events that led to a major crisis.

他的到来引发了一连串令人惊讶的事件。

His arrival set off a surprising ___chain of events.

这项政策变化在整个行业引发了一场意想不到的连锁反应。

The policy change triggered an unexpected ___chain reaction across the industry.