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.

只有授权人员才能用他们的钥匙打开这道闸门。

Only authorised personnel can open the ___barrier with their keys.

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.