barrier

尽管存在语言障碍，他们很快就成了好朋友。

Despite the language ___barrier, they soon became good friends.

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.