plain curve

例句：

1. 1.The engineer drew a plain curve on the map.
   工程师在地图上画了一条直线。
2. 2.The car made a plain curve in the road.
   汽车在公路上做了一个直线弯。
3. 3.The driver followed the plain curve of the road.
   司机沿着道路的直线弯行驶。