这个防火墙可以阻止未经授权的访问，只允许通过安全网关进入系统。

This firewall blocks unauthorized access and only allows entry through secure ___gateways.

这座宏伟的石拱门是通往皇宫的主要入口。

The grand stone ___gateway serves as the main entrance to the royal palace.

掌握外语技能是通往国际就业市场的桥梁。

Mastering foreign languages serves as ___gateways to international job markets.