活动中设立了一个临时栅栏来控制人群。

A temporary ___barrier was set up to control the crowd at the event.

他翻过金属护栏回到了赛道上。

He climbed over the metal ___barrier to get back onto the racetrack.

请在安全护栏后等待，直到游乐设施完全停下。

Please wait behind the safety ___barrier until the ride comes to a complete stop.