line center

例句：

1. 1.The line center is the key to the puzzle.
   线心是解开谜题的关键。
2. 2. The center of the circle is the point where it touches the ground.
   圆的中心是它与地面接触的点。
3. 3.The line center is used to determine the length of the object.
   线心用于确定物体的长度。