directed line segment

例句：

1. 1. The engineer drew a directed lineto indicate the path of the road.
   工程师画了一条有向线来指示道路的路径。
2. 2. The scientist used a directed lineto measure the length of the object.
   科学家使用一条有向线来测量物体的长度。
3. 3. The architect designed a directed line thatwould guide the construction workers.
   建筑师设计了一条有向线，以指导建筑工人的工作。