当温度超过临界值时，警报就会响起。

The alarm will sound when the temperature exceeds the ___threshold.

他站在门口犹豫了一会儿才跨过门槛。

He hesitated for a moment before stepping over the ___threshold.

当温度达到设定阈值时，空调会自动开启。

The air conditioner turns on automatically when the temperature reaches the set ___threshold.