upper curve

例句：

1. 1. The upper curve of the road is quite steep.
   这条路的上曲线相当陡峭。
2. 2.The upper curve of the mountain is visible from a distance.
   从远处可以看到这座山的上曲线。
3. 3. The upper curve of the river is where the rapids are located.
   河流的上曲线是急流所在的地方。