wave trough tectonic belts

例句：

1. 1.The river flows through a deep trough in the mountains.
   这条河在山区流过一个深深的谷地。
2. 2.The farmer had to dig a trough for his cows.
   农民不得不为他的牛挖一条沟。
3. 3. The trough is filled with water and fish.
   这个沟里装满了水和鱼。