linear differential operator

例句：

1. 1. The path is linear and straight.
   这条路线是直线的。
2. 2. The data is linearly proportional to the input.
   数据与输入呈线性比例关系。
3. 3. The graph shows a linear relationship between temperature and rainfall.
   图表显示温度和降雨量之间存在线性关系。