trigger

He kept his finger on the trigger but did not fire the weapon.

(Chinese) 他的手指一直扣在扳机上，但没有开火。

The trigger of this old rifle is very stiff and hard to pull.

(Chinese) 这支旧步枪的扳机非常紧，很难扣动。

The loud noise triggered a panic among the birds in the trees.

(Chinese) 巨大的响声引发了树上鸟群的恐慌。

Certain types of pollen can trigger a severe allergic reaction in some people.

(Chinese) 某些种类的花粉可能会在部分人群中引发严重的过敏反应。