channel purlin

例句：

1. 1. The river is the main channel of transportation in this region.
   这条河流是该地区的主要交通干线。
2. 2.He used to travel by train as a child but now he prefers taking the bus.
   他小时候坐火车旅行，但现在他更喜欢坐公共汽车。
3. 3. The new highway will connect two cities and provide a better channel for trade.
   新的高速公路将连接两个城市，为贸易提供更好的通道。