linear air track

例句：

1. 1. The path islinear and easy to follow.
   这条路线是直线的，很容易跟随。
2. 2. Thedata is linearly proportionalto the input.
   数据与输入成正比例关系。
3. 3. The project was designedwith a linear layout.
   该项目设计为直线布局。