straight tunnel portal

例句：

1. 1.The tunnel is straight and leads to the exit.
   这条隧道直通出口。
2. 2. The portal is designed to allow easy access to the main building.
   这个入口设计得便于进入主楼。
3. 3. The tunnel was built for emergency vehicles to avoid congestion.
   这条隧道是为紧急车辆修建的，以避免拥堵。